Active material, method of manufacturing the same, electrode, and secondary battery

ABSTRACT

An active material includes, as constituent elements, silicon, oxygen, a first element, a second element, and a third element. The first element includes boron, phosphorus, or both. The second element includes at least one of an alkali metal element, a transition element, or a typical element. The typical element excludes silicon, oxygen, boron, phosphorus, an alkali metal element, and an alkaline earth metal element. The third element includes an alkaline earth metal element. The content of silicon with respect to all the constituent elements excluding oxygen and carbon is 60 at % or greater and 98 at % or less. The content of the first element with respect to all the constituent elements excluding oxygen and carbon is 1 at % or greater and 25 at % or less. The content of the second element with respect to all the constituent elements excluding oxygen and carbon is 1 at % or greater and 34 at % or less. The content of the third element with respect to all the constituent elements excluding oxygen and carbon is 0 at % or greater and 6 at % or less. A first peak is detected in an XPS spectrum of Si2p relating to the active material. The XPS spectrum of Si2p is measured using X-ray photoelectron spectroscopy (XPS). The first peak includes an apex within a range of a binding energy of 102 eV or greater and 105 eV or less, and a shoulder on a smaller binding energy side of the apex. A second peak is detected in a Raman spectrum relating to the active material. The Raman spectrum is measured using Raman spectroscopy. The second peak includes an apex within a range of a Raman shift of 435 cm −1  or greater and 465 cm −1  or less.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of PCT application no.PCT/JP2020/034059 filed on Sep. 9, 2020, which claims priority toJapanese patent application no. JP2019-174299 filed on Sep. 25, 2019,the entire contents of which are being incorporated by reference.

BACKGROUND

The present technology relates to an active material including siliconand oxygen as constituent elements, a method of manufacturing the activematerial, an electrode including the active material, and a secondarybattery including the active material.

Various electronic apparatuses such as mobile phones have been widelyused. Such widespread use has promoted the development of a secondarybattery that is smaller in size and lighter in weight and allows for ahigher energy density, as a power source. The secondary battery includeselectrodes, i.e., a positive electrode and a negative electrode, and anelectrolytic solution. The electrodes include an active materialcontributing to an electrode reaction. A configuration of the secondarybattery influences a battery characteristic. Accordingly, theconfiguration of the secondary battery has been considered in variousways.

For example, silicon dioxide is heated to generate a silicon oxide gas,following which the silicon oxide gas is condensed into silicon oxide(SiO_(x)) powder. To improve a cyclability characteristic or othercharacteristics of a secondary battery including silicon oxide as anegative electrode active material, different elements are added to thesilicon oxide. To obtain the negative electrode active material forhigh-capacity applications, a pyroxene silicic acid compound and areduced product of tin oxide (SnO_(x)) acquired as a result of heatreduction using a reducing gas are used.

SUMMARY

The present disclosure relates to an active material including siliconand oxygen as constituent elements, a method of manufacturing the activematerial, an electrode including the active material, and a secondarybattery including the active material.

Although consideration has been given in various ways to improve abattery characteristic of the secondary battery, the batterycharacteristic of the secondary battery still remains insufficient.Accordingly, there is still room for improvement in terms of the batterycharacteristic of the secondary battery.

The technology of the present disclosure has been made in view of suchan issue, and thus to provide, for example, an active material, a methodof manufacturing the active material, an electrode, and a secondarybattery that are each able to achieve a superior battery characteristicaccording to an embodiment.

An active material according to an embodiment of the technology includessilicon (Si), oxygen (O), a first element, a second element, and a thirdelement as constituent elements. The first element includes boron (B),phosphorus (P), or both. The second element includes at least one of analkali metal element, a transition element, or a typical element. Thetypical element excludes silicon, oxygen, boron, phosphorus, an alkalimetal element, and an alkaline earth metal element. The third elementincludes an alkaline earth metal element. The content of silicon withrespect to all the constituent elements excluding oxygen and carbon (C)is 60 at % or greater and 98 at % or less. The content of the firstelement with respect to all the constituent elements excluding oxygenand carbon is 1 at % or greater and 25 at % or less. The content of thesecond element with respect to all the constituent elements excludingoxygen and carbon is 1 at % or greater and 34 at % or less. The contentof the third element with respect to all the constituent elementsexcluding oxygen and carbon is 0 at % or greater and 6 at % or less. Afirst peak is detected in an XPS spectrum of Si2p relating to the activematerial. The XPS spectrum of Si2p is measured using X-ray photoelectronspectroscopy (XPS) and defined by a horizontal axis indicating a bindingenergy (eV) and a vertical axis indicating a spectrum intensity. Thefirst peak includes an apex within a range of the binding energy of 102eV or greater and 105 eV or less, and a shoulder on a smaller bindingenergy side of the apex. A second peak is detected in a Raman spectrumrelating to the active material. The Raman spectrum is measured usingRaman spectroscopy and defined by a horizontal axis indicating a Ramanshift (cm⁻¹) and a vertical axis indicating a spectrum intensity. Thesecond peak includes an apex within a range of the Raman shift of 435cm⁻¹ or greater and 465 cm⁻¹ or less.

A method of manufacturing an active material according to an embodimentof the technology includes: preparing silicate glass including, asconstituent elements, silicon (Si), oxygen (O), a first elementincluding boron (B), phosphorus (P), or both, a second element includingat least one of an alkali metal element, a transition element, or atypical element excluding silicon, oxygen, boron, phosphorus, an alkalimetal element, and an alkaline earth metal element, and a third elementincluding an alkaline earth metal element; mixing the silicate glasswith a carbon source to thereby obtain a mixture of the silicate glassand the carbon source; and heating the mixture to thereby manufacture anactive material including silicon, oxygen, the first element, the secondelement, and the third element as constituent elements. In the activematerial, the content of silicon with respect to all the constituentelements excluding oxygen and carbon (C) is 60 at % or greater and 98 at% or less. The content of the first element with respect to all theconstituent elements excluding oxygen and carbon is 1 at % or greaterand 25 at % or less. The content of the second element with respect toall the constituent elements excluding oxygen and carbon is 1 at % orgreater and 34 at % or less. The content of the third element withrespect to all the constituent elements excluding oxygen and carbon is 0at % or greater and 6 at % or less.

An electrode according to an embodiment of the technology includes anactive material. The active material has a configuration similar to theconfiguration of the active material according to the embodiment of thetechnology described above.

A secondary battery according to an embodiment of the technologyincludes a positive electrode, a negative electrode, and an electrolyticsolution. The negative electrode includes a negative electrode activematerial. The negative electrode active material has a configurationsimilar to the configuration of the active material according to anembodiment of the technology.

According to the active material, the electrode, or the secondarybattery of the embodiment of the technology, the active material, i.e.,the negative electrode active material, includes silicon, oxygen, thefirst element, the second element, and the third element as constituentelements, and the content of each of the constituent elements satisfiesthe condition described above. Further, the first peak described aboveis detected in the XPS spectrum of Si2p relating to the active materialmeasured using X-ray photoelectron spectroscopy, and the second peakdescribed above is detected in the Raman spectrum relating to the activematerial measured using Raman spectroscopy. Accordingly, it is possibleto obtain a superior battery characteristic.

According to the method of manufacturing the active material of anembodiment of the technology, the silicate glass including silicon,oxygen, the first element, the second element, and the third element asconstituent elements is mixed with the carbon source, following whichthe mixture of the silicate glass and the carbon source is heated tothereby manufacture the active material. The content of each of theconstituent elements in the active material satisfies the conditiondescribed above. Accordingly, it is possible to obtain an activematerial achieving a superior battery characteristic.

Note that effects of the technology are not necessarily limited to theeffects described above and may include any of a series of suitableeffects including described below in relation to the technologyaccording to an embodiment.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view of a configuration of an active materialaccording to an embodiment of the technology.

FIG. 2 is an example of a result of analysis (an XPS spectrum of Si2p)of the active material using XPS.

FIG. 3 is an example of a result of analysis (a Raman spectrum) of theactive material using Raman spectroscopy.

FIG. 4 is a flowchart for describing a method of manufacturing theactive material according to an embodiment of the technology.

FIG. 5 is a perspective view of configurations of an electrode and asecondary battery of a laminated-film type according to an embodiment ofthe technology.

FIG. 6 is a sectional view of a configuration of a wound electrode bodyillustrated in FIG. 5.

FIG. 7 is a plan view of respective configurations of a positiveelectrode and a negative electrode illustrated in FIG. 6.

FIG. 8 is a sectional view of configurations of another electrode andanother secondary battery of a cylindrical type according to oneembodiment of the technology.

FIG. 9 is a perspective view of a configuration of a secondary batteryof another laminated-film type according to Modification 2.

FIG. 10 is a sectional view of a configuration of a stacked electrodebody illustrated in FIG. 9.

FIG. 11 is a block diagram illustrating a configuration of anapplication example of the secondary battery, which is a battery packincluding a single battery.

FIG. 12 is a block diagram illustrating a configuration of anapplication example of the secondary battery, which is a battery packincluding an assembled battery.

FIG. 13 is a block diagram illustrating a configuration of anapplication example of the secondary battery, which is an electricvehicle.

FIG. 14 is a sectional view of a configuration of a secondary battery ofa coin type for testing.

DETAILED DESCRIPTION

One or more embodiments of the technology of the present disclosure aredescribed below in detail with reference to the drawings.

First, a description is given of an active material according to anembodiment of the technology. Note that a manufacturing method of anactive material according to an embodiment of the technology is amanufacturing method of the active material described herein, and istherefore descried below together.

The active material is a material contributing to an electrode reaction.More specifically, the active material is a material into which anelectrode reactant is insertable and from which an electrode reactant isextractable. The active material is used as an electrode material of adevice that is operable using the electrode reaction. In this case, theelectrode reactant is inserted into the active material or extractedfrom the active material in an ionic state. Note that the activematerial may be used as an electrode material for a positive electrode(a positive electrode active material) or an electrode material for anegative electrode (a negative electrode active material).

Applications of the active material are not limited to particularapplications as long as they are devices that are operable using anelectrode reaction. Specifically, examples of the applications of theactive material include a battery and a capacitor. Note that the batterymay be a primary battery or a secondary battery.

The electrode reactant is not limited to a particular kind and may be alight metal such as an alkali metal, an alkaline earth metal, oraluminum. Examples of the alkali metal include lithium, sodium, andpotassium, and examples of the alkaline earth metal include beryllium,magnesium, and calcium.

First, a description is given of a configuration of the active material.FIG. 1 illustrates a sectional configuration of an active material 100,which is an example of the active material.

As illustrated in FIG. 1, the active material 100 includes a center part101 and a covering part 102. Note that the center part 101 has aspherical three-dimensional shape in FIG. 1 for simple illustration;however, the three-dimensional shape of the center part 101 is notlimited to a particular shape.

The center part 101 is a main part of the active material 100 into whichthe electrode reactant is inserted and from which the electrode reactantis extracted. The center part 1101 includes carbon-reduced silicateglass. Unlike ordinary silicate glass (hereinafter simply referred to as“silicate glass”), the carbon-reduced silicate glass is formed by acarbon reduction treatment on silicate glass using a carbon source as areducing agent, as to be described later. Note that only one kind of thecarbon-reduced silicate glass may be included, or two or more kinds ofthe carbon-reduced silicate glass may be included.

In the carbon-reduced silicate glass formed by the carbon reductiontreatment, a reduction reaction of the silicate glass which is a rawmaterial is facilitated due to the use of the carbon source as thereducing agent. This allows the silicate glass to be so reduced(activated) that the electrode reactant is sufficiently inserted andextracted from the silicate glass. That is, the silicate glass is hardlyreduced by an ordinary reduction treatment in which a reducing gas isused as a reducing agent, whereas the silicate glass is sufficientlyreduced in a special reduction treatment, i.e., the carbon reductiontreatment, in which the carbon source is used as a reducing agent. Thus,the carbon-reduced silicate glass has a physical property different fromthe physical property of silicate glass. Details of the physicalproperty of the carbon-reduced silicate glass will be described later.

Specifically, the carbon-reduced silicate glass includes silicon,oxygen, a first element, a second element, and a third element, asconstituent elements.

The content of each constituent element with respect to all theconstituent elements excluding oxygen and carbon in the carbon-reducedsilicate glass is set within a predetermined range. In a case where thetotal content of all the constituent elements excluding oxygen andcarbon is assumed to be 100 at %, the content of each constituentelement represents the atomic percent of the content of the constituentelement. Note that the content (atomic percent) of each constituentelement is measured by analyzing the carbon-reduced silicate glass usingscanning electron microscope (SEM) and energy dispersive X-rayspectroscopy (EDX) spectrometry.

(Silicon)

Silicon is a primary constituent element of the carbon-reduced silicateglass. The content of silicon with respect to all the constituentelements excluding oxygen and carbon is from 60 at % to 98 at % bothinclusive.

Oxygen is another primary constituent element of the carbon-reducedsilicate glass that forms an oxide with silicon. Thus, thecarbon-reduced silicate glass includes SiO_(x) (where x satisfies 0≤x≤2)as a primary component. The SiO_(x) is supposed to include nano silicon(Si) dispersed in amorphous silicon dioxide (SiO₂). Alternatively, theSiO_(x) is supposed to include, in the glass component, silicon intowhich electrode reactant is sufficiently insertable and from whichelectrode reactant is sufficiently extractable.

The first element includes one or more network-forming elements. Morespecifically, the first element includes boron, phosphorus, or both. Areason for this is that silicate glass including the first element inaddition to silicon and oxygen as constituent elements is easily andsufficiently reduced in the carbon reduction treatment. This facilitateseasy and stable formation of the carbon-reduced silicate glass in thecarbon reduction treatment.

The term “network-forming element” is a generic term for a series ofelements capable of forming a network-forming body (network-formingoxide). The first element may thus include, for example, germanium (Ge)in addition to boron and phosphorus described above.

The content of the first element with respect to all the constituentelements excluding oxygen and carbon is from 1 at % to 25 at % bothinclusive. A reason for this is that the silicate glass is easily andsufficiently reduced in the carbon reduction treatment.

Note that, in a case where the first element includes two or moreelements, the content of the first element is the sum of the contents ofthese elements. Likewise, in a case where the second or third elementincludes two or more elements, the content of the second or thirdelement to be described later is the sum of the contents of theseconstituent elements.

The second element includes one or more of an alkali metal element, atransition element, and a typical element. A reason for this is that,unlike the third element to be described later, the second elementhardly affects the reducibility of the silicate glass in the carbonreduction treatment even if included in the silicate glass as aconstituent element. Accordingly, the silicate glass is sufficientlyreduced in the carbon reduction treatment even if the second element isincluded in the silicate glass as a constituent element.

The term “alkali metal element” is a generic term for a series ofelements belonging to the Group 1 in the long period periodic table.Specifically, examples of the alkali metal element include lithium (Li),sodium (Na), and potassium (K).

The term “transition element” is a generic term for a series of elementsbelonging to any of Groups 3 to 11 in the long period periodic table.Specifically, examples of the transition element include scandium (Sc),titanium (Ti), zirconium (Zr), and cerium (Ce). However, the transitionelement is not limited to a particular kind as long as the transitionelement belongs to any of Groups 3 to 11 in the long period periodictable. Thus, the examples of the transition element may further includeelements including, without limitation, lanthanum (La), hafnium (Hf),tantalum (Ta), and tungsten (W) other than the series of elements suchas scandium described above.

The term “typical element” is a generic term for a series of elementsbelonging to any of Groups 1, 2, and 12 to 18 in the long periodperiodic table. However, silicon, oxygen, boron, phosphorus, an alkalimetal element, and an alkaline earth metal element are excluded from thetypical element described here. Thus, examples of the typical elementdescribed here include aluminum (Al), sulfur (S), chlorine (Cl), zinc(Zn), and bismuth (Bi). However, the typical element is not limited to aparticular kind as long as the typical element belongs to any of Groups1, 2, and 12 to 18 in the long period periodic table. Thus, the examplesof the typical element may further include elements including, withoutlimitation, antimony (Sb) other than the series of elements such asaluminum described above.

The content of the second element with respect to all the constituentelements excluding oxygen and carbon is from 1 at % to 34 at % bothinclusive. A reason for this is that the silicate glass is easily andsufficiently reduced in the carbon reduction treatment even if thesecond element is included in the silicate glass as a constituentelement.

The third element is an optional constituent element of thecarbon-reduced silicate glass. The carbon-reduced silicate glass maythus include the third element as a constituent element or may notinclude the third element as a constituent element.

The third element includes one or more alkaline earth metal elements.The term “alkaline earth metal element” is a generic term for a seriesof elements belonging to Group 2 in the long period periodic table.Specifically, examples of the third element include magnesium (Mg),calcium (Ca), strontium (Sr), and barium (Ba).

Note that the content of the third element with respect to all theconstituent elements excluding oxygen and carbon is from 0 at % to 6 at% both inclusive.

The reason why the lower limit of the content of the third element is 0at % is that the carbon-reduced silicate glass may not include the thirdelement as a constituent element since the third element is an optionalconstituent element of the carbon-reduced silicate glass, as describedabove.

The reason why the upper limit of the content of the third element is 6at % is that the content of the third element should be within a rangethat does not affect the reducibility of the silicate glass in thecarbon reduction treatment since the third element affects thereducibility of the silicate glass in the carbon reduction process, asdescribed above.

Specifically, in a case where the content of the third element isgreater than 6 at %, the silicate glass is hardly reduced in the carbonreduction treatment because the amount of the third element present inthe silicate glass is excessively large. As a result, substantially nocarbon-reduced silicate glass is manufactured. In contrast, in a casewhere the content of the third element is 6 at % or less, the silicateglass is easily reduced in the carbon reduction treatment because theamount of the third element present in the silicate glass isappropriately decreased. As a result, the carbon-reduced silicate glassis substantially manufactured.

The covering part 102 covers a portion or all of a surface of the centerpart 101. Note that, in a case where the covering part 102 covers aportion of the surface of the center part 101, a plurality of locationsseparated from each other on the surface of the center part 101 may becovered with the covering parts 102.

The covering part 102 includes carbon as a constituent element to havean electrically conductive property. A reason for this is that theelectrically conductive property of the active material 100 as a wholeenhances in a case where the surface of the center part 101 is coveredwith the covering part 102 having an electrically conductive property,as compared with a case where the surface of the center part 101 is notcovered with the covering part 102. A material included in the coveringpart 102 is not limited to a particular material as long as carbon isincluded therein as a constituent element.

Specifically, the covering part 102 is formed as a coating film coveringthe surface of the center part 101 as a result of thermal decompositionof a carbon source (a mixture of silicate glass and a reducing agent)when the carbon source is heated in a manufacturing process of theactive material (carbon reduction treatment) as to be described later.In this case, the covering part 102 may include the carbon source as itis, may include a decomposition product of the carbon source (organicsubstance decomposition carbon), or may include both of them.

The thickness of the covering part 102 is not limited to a particularthickness. A reason for this is that the electrically conductiveproperty of the active material 100 as a whole enhances in a case wherethe covering part 102 is present even in a slight amount on the surfaceof the center part 101, as compared with a case where the covering part102 is not present at all on the surface of the center part 101.

Next, a description is given of physical properties of the activematerial 100. In the following, two physical properties are described inorder that are specified on the basis of the results of analyses of theactive material 100 using X-ray photoelectron spectroscopy (XPS) andRaman spectroscopy.

FIG. 2 illustrates an example of a result of the analysis (an XPSspectrum of Si2p) of the active material 100 using XPS for describing afirst physical property. The XPS spectrum is defined by a horizontalaxis representing the binding energy (eV), and a vertical axisrepresenting the spectrum intensity. Note that the result of theanalysis using XPS described here is an analysis result obtained afterargon (Ar) ion sputtering for a sputtering time of 1000 seconds.

FIG. 2 also illustrates an XPS spectrum of the silicate glass indicatedwith a dashed line in addition to the XPS spectrum of the carbon-reducedsilicate glass indicated with a solid line. That is, the carbon-reducedsilicate glass of which XPS spectrum is detected as indicated with thesolid line is obtainable by conducting the carbon reduction treatment onthe silicate glass of which XPS spectrum is detected as indicated withthe dashed line. Note that shading is applied to the range of thebinding energy from 102 eV to 105 eV both inclusive.

As illustrated in FIG. 2, the carbon-reduced silicate glass has aphysical property different from the physical property of the silicateglass in terms of the result of analysis using XPS or the shape of theXPS spectrum.

Specifically, a peak XA (first peak) is detected in the solid-line XPSspectrum relating to the carbon-reduced silicate glass. The peak XA hasan apex XAT within the range of the binding energy from 102 eV to 105 eVboth inclusive, and a shoulder XAS on a smaller binding energy side ofthe apex XAT (i.e., on the right side in FIG. 2). The shoulder XAS is ashoulder-like portion protruding toward the low binding energy side froma portion of the middle of the peak XA having the apex XAT. That is, theshoulder XAS is a stepped portion.

In contrast, a peak XB is detected in the dashed-line XPS spectrumrelating to the silicate glass. The peak XB has an apex XBT within therange of the binding energy from 102 eV to 105 eV both inclusive, butdoes not have a shoulder corresponding to the shoulder XAS on a smallerbinding energy side of the apex XBT.

The following tendencies are derived from these results of the analysisof the active material 100 using XPS or the shapes of XPS spectra.Regarding the carbon-reduced silicate glass, the peak XA having the apexXAT and the shoulder XAS is detected because silicate glass, which isthe raw material of the carbon-reduced silicate glass, has beensufficiently reduced by the carbon reduction treatment. In contrast,regarding the silicate glass, the peak XB having only the apex XBT isdetected because the silicate glass has not been subjected to the carbonreduction treatment yet.

Accordingly, it is possible to identify which of the carbon-reducedsilicate glass or the silicate glass the analyte is on the basis of theresults of analysis using XPS. The carbon-reduced silicate glassmanufactured by the carbon reduction treatment therefore differs inphysical property from the silicate glass in that the above-describedcondition is satisfied in terms of XPS.

Likewise, it is possible to identify the center part 101 of the activematerial 100 by the above-described identification method. That is, thecenter part 101 includes the carbon-reduced silicate glass in a casewhere the peak XA is detected by the analysis of the center part 101using XPS, whereas the center part 101 includes the silicate glass in acase where the peak XB is detected.

Note that the silicate glass is hardly reduced by the ordinary reductiontreatment, as described above. Accordingly, even if the ordinaryreduction treatment is performed using the silicate glass, the silicateglass is hardly reduced and expected to exhibit the peak XB rather thanthe peak XA.

Here, the peak XA relating to the carbon-reduced silicate glass has theshoulder XAS, whereas the peak XB relating to the silicate glass has noshoulder, as described above. Accordingly, it is also possible toidentify which of the carbon-reduced silicate glass or the silicateglass the analyte is by the following methods.

First, the width of the middle of the peak XA in a height direction islarger than the width of the middle of the peak XB in the heightdirection. The half-width of the peak XA is therefore larger than thehalf-width of the peak XB. More specifically, the half-width of the peakXA is 4.0 eV or greater. Although the half-width of the peak XA is 4.0eV or greater, the half-width of the peak XB is not 4.0 eV or greater.Accordingly, it is also possible to identify which of the reducedsilicate glass or the silicate glass the analyte is by measuring thehalf-width instead of examining the presence or absence of the shoulderXAS. That is, it is possible to identify the kind of the analyte bymeasuring the half width even in a case where it is difficult todetermine the presence or absence of the shoulder XAS because theshoulder XAS is small.

Second, the area of the middle of the peak XA is larger than the area ofthe middle of the peak XB. Accordingly, in a case where each of thepeaks XA and XB is decomposed into five Si-attributed peaks (a Si⁰ peak,a Si¹⁺ peak, a Si²⁺ peak, a Si³⁺ peak, and a Si⁴⁺ peak), the area ratioS2/S1 of the peak XA is larger than the area ratio S2/S1 of the peak XB.More specifically, the area ratio S2/S1 of the peak XA is 0.85 orgreater.

Here, the area S1 is the area of the Si⁴⁺ peak, while the area S2 is thesum of the area of the Si⁰ peak, the area of the Si¹⁺ peak, the area ofthe Si²⁺ peak, and the area of the Si⁴⁺ peak. Each of the areas S1 andS2 may be calculated using an analysis (arithmetic) function of an XPSdevice.

Although the area ratio S2/S1 of the peak XA is 0.85 or greater, thearea ratio S2/S1 of the peak XB is not 0.85 or greater. Accordingly, itis also possible to identify which of the reduced silicate glass or thesilicate glass the analyte is by measuring the area ratio S2/S1 insteadof examining the presence or absence of the shoulder XAS. That is, it ispossible to identify the kind of the analyte by measuring the half widtheven in a case where it is difficult to determine the presence orabsence of the shoulder XAS because the shoulder XAS is small, asdescribed above.

FIG. 3 illustrates an example of a result of the analysis (a Ramanspectrum) of the active material 100 using Raman spectroscopy fordescribing a second physical property. The Raman spectrum is defined bya horizontal axis representing the Raman shift (cm⁻¹) and a verticalaxis representing the spectrum intensity.

FIG. 3 also illustrates a Raman spectrum of the silicate glass indicatedwith a dashed line in addition to the Raman spectrum of thecarbon-reduced silicate glass indicated with a solid line. That is, thecarbon-reduced silicate glass of which Raman spectrum is detected asindicated with the solid line is obtainable by conducting the carbonreduction treatment on the silicate glass of which Raman spectrum isdetected as indicated with the dashed line. Note that shading is appliedto the range of the Raman shift from 435 cm⁻¹ to 465 cm⁻¹ bothinclusive.

As illustrated in FIG. 3, the carbon-reduced silicate glass has aphysical property different from the physical property of the silicateglass in terms of the result of analysis using Raman spectroscopy or theshape of the Raman spectrum.

Specifically, a peak RA (second peak) is detected in the solid-lineRaman spectrum relating to the carbon-reduced silicate glass. The peakRA has an apex RAT within the range of the Raman shift from 435 cm⁻¹ toof 465 cm⁻¹ both inclusive.

In contrast, a peak RB is detected in the dashed-line Raman spectrumrelating to the silicate glass. The peak RB has an apex RBT outside therange of the binding energy from 435 cm⁻¹ to 465 cm⁻¹ both inclusiverather than within the range. Specifically, the peak RB has the apex RBTwithin the range of the binding energy from 470 cm⁻¹ to 490 cm⁻¹ bothinclusive. Note that, just for reference, a peak having an apex withinthe range of the binding energy from 510 cm⁻¹ to 525 cm⁻¹ both inclusiveis detected in the Raman spectrum relating to a single substance ofsilicon having crystallinity.

The following tendencies are derived from these results of the analysisof the active material 100 using Raman spectroscopy or the shape ofRaman spectrum. Regarding the carbon-reduced silicate glass, the peak RAhaving the apex RAT within the range from 435 cm⁻¹ to 465 cm⁻¹ bothinclusive is detected because silicate glass, which is the raw materialof the carbon-reduced silicate glass, has been sufficiently reduced bythe carbon reduction treatment. In contrast, regarding the silicateglass, the peak RB having the apex RBT outside the above-described rangeis detected because the silicate glass has not been subjected to thecarbon reduction treatment yet. The carbon-reduced silicate glassmanufactured by the carbon reduction treatment therefore differs inphysical property from the silicate glass in that the above-describedcondition is satisfied in terms of Raman spectroscopy.

Likewise, it is possible to identify the center part 101 of the activematerial 100 by the above-described identification method. That is, thecenter part 101 includes the carbon-reduced silicate glass in a casewhere the peak RA is detected by the analysis of the center part 101using Raman spectroscopy, whereas the center part 101 includes thesilicate glass in a case where the peak RB is detected.

Note that the silicate glass is hardly reduced by the ordinary reductiontreatment, as described above. Accordingly, even if the ordinaryreduction treatment is performed using the silicate glass, the silicateglass is hardly reduced and expected to exhibit the peak RB rather thanthe peak RA.

These results indicate that, in the case of the carbon-reduced silicateglass, the peak XA is detected in the XPS spectrum of Si2p measuredusing XPS, and the peak RA is detected in the Raman spectrum measuredusing Raman spectroscopy. Thus, the active material 100 includes thecarbon-reduced silicate glass in a case where both of the peaks XA andRA described above are detected by analyzing the active material 100(the center part 101) using both XPS and Raman spectroscopy.

In contrast, the active material 100 does not include the carbon-reducedsilicate glass in a case where the peak XA, the peak RA, or both are notdetected by analyzing the active material 100 using both XPS and Ramanspectroscopy.

The reduced silicate glass included in the active material 100 (thecenter part 101) satisfies the two physical property conditions relatingto XPS and Raman spectroscopy described above because the crystallinityof a glass material including the above-described SiO_(x) as a primarycomponent is optimized due to the reduction reaction of the reducedsilicate glass which proceeds more easily than that of silicate glass.This makes it easy for the electrode reactants to be sufficiently andstably inserted into or extracted from the active material 100, and alsocontinuously makes it easy for the electrode reactant to be insertedinto or extracted from the active material 100 even if the electrodereaction is repeated.

Next, a description is given of a method of manufacturing the activematerial 100. FIG. 4 is a flowchart for describing the method ofmanufacturing the active material 100. Step numbers in parenthesesdescribed below correspond to step numbers illustrated in FIG. 4.

In a case of manufacturing the active material 100, first, powder ofsilicate glass is prepared as a raw material (Step S1). In this case,previously synthesized silicate glass may be acquired by a method suchas purchase, or silicate glass may be synthesized by a user.

The silicate glass does not satisfy the two physical property conditionsrelating to XPS and Raman spectroscopy described above because thesilicate glass has not been subjected to the carbon reduction treatmentyet. Except this point, the silicate glass has a configurationsubstantially similar to that of the carbon-reduced silicate glass. Thatis, the silicate glass includes silicon, oxygen, the first element, thesecond element, and the third element as constituent elements. Detailsof each of the first element, the second element, and the third elementare as described above.

Note that, in a case of synthesizing the silicate glass, silicon dioxide(SiO₂) is mixed with respective sources of the first element, the secondelement, and the third element, following which the mixture is heated.Conditions including, without limitation, a heating temperature and aheating time may be set to any values.

These sources are compounds including respective constituent elements.The compounds are not limited to particular kinds. Specifically, thecompounds are, for example, oxides of the respective constituentelements. That is, examples of the source of the first element includeboron trioxide (B₂O₅) and phosphorus pentoxide (P₂O₅). Examples of thesource of the second element include sodium oxide (Na₂O), potassiumoxide (K₂O), scandium oxide (ScO), titanium oxide (TiO₂), zirconiumoxide (Zr₂O), cerium oxide (CeO), hafnium oxide (HfO₂), tantalum oxide(Ta₂O₅), tungsten oxide (WO₃), aluminum oxide (Al₂O₃), phosphoruspentasulfide (P₂S₅), lithium sulfide (Li₂S), magnesium sulfide (MgS),silicon tetrachloride (SiCl₄), zinc oxide (ZnO₂), bismuth oxide (BiO),and antimony oxide (Sb₂O₃). Examples of the source of the third elementinclude magnesium oxide (MgO), calcium oxide (CaO), strontium oxide(SrO), and barium oxide (BaO).

The silicon dioxide and the respective sources of the first element, thesecond element, and the third element are thereby mixed with each otherto form a solid solution. A glass body is thereby formed which includessilicon, oxygen, the first element, the second element, and the thirdelement as constituent elements. As a result, the silicate glass issynthesized.

After preparing the silicate glass, the silicate glass is mixed with acarbon source to obtain a mixture (Step S2). The term “carbon source” isa generic term for a material usable as a source of carbon.Specifically, the carbon source includes, without limitation, one ormore of carbon materials and carbonizable organic substances. In otherwords, only a carbon material may be used, only a carbonizable organicsubstance may be used, or both of them may be used as the carbon source.Examples of the carbon material include non-fibrous carbon and fibrouscarbon. Examples of the non-fibrous carbon include carbon black, andexamples of the fibrous carbon include carbon nanotubes and carbonnanofibers. Examples of the carbonizable organic substance includesaccharides and polymer compounds. Examples of the saccharide includesucrose, maltose, and cellulose. Examples of the polymer compoundsinclude polyimide, polyvinylidene difluoride, polymethyl methacrylate,polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid. A reasonwhy such a material is used as the carbon source is that the silicateglass is sufficiently reduced in the carbon reduction treatment. Anotherreason is that the covering part 102 having a sufficient electricallyconductive property is easily and stably formed by using the carbonsource, as to be described later.

In this case, the mixture may be stirred using a stirring device.Conditions including, without limitation, a stirring speed and astirring time may be set to any values.

Alternatively, a mixture in a paste state may be obtained by addingmaterials including, without limitation, a binder and a solvent to themixture. In this case, it is preferable to stir the mixture using thestirring device described above. The binder is not limited to aparticular kind, and may be one or more polymer compounds including,without limitation, polyvinylidene difluoride, polyimide, and polymethylmethacrylate. The solvent is not limited to a particular kind, and maybe one or more of organic solvents including, without limitation,N-methyl-2-pyrrolidone. Note that a binder solution in which a binder ispreviously dissolved in a solvent may be used.

Lastly, the mixture is heated (Step S3). In this case, one or more ofheating devices including, without limitation, an oven may be used.Conditions including, without limitation, a heating temperature and aheating time may be set to any values. Specifically, the heatingtemperature is from 700° C. to 1400° C. both inclusive, and the heatingtime is from one hour to twenty hours both inclusive.

In a case where a mixture including a binder is used, the mixture may beheated in two stages. Specifically, first, the mixture is subjected tofirst heating to dry the mixture. Although the condition of the firstheating is not limited to a particular condition, the heatingtemperature is from 40° C. to 500° C. both inclusive, and the heatingtime is from 10 minutes to three hours both inclusive. Thereafter, thedried mixture is pulverized. Lastly, the pulverized mixture is subjectedto second heating. Although the condition of the second heating is notlimited to a particular condition, the heating temperature is from 700°C. to 1200° C. both inclusive, and the heating time is from one hour totwenty hours both inclusive.

The silicate glass is thereby subjected to the carbon reductiontreatment, and the silicate glass is sufficiently reduced using thecarbon source as a reducing agent. In other words, the crystalline stateof SiO_(x) is so optimized that the electrode reactant is allowed to besufficiently inserted and extracted. Accordingly, carbon-reducedsilicate glass is synthesized that includes SiO_(x) as a primarycomponent. As a result, the center part 101 is formed that includes thecarbon-reduced silicate glass.

In addition, carbon (organic substance decomposition carbon) adheres tothe surface of the center part 101 in the carbon reduction treatment dueto thermal decomposition of the carbon source used as the reducingagent, as described above. As a result, the covering part 102 includingcarbon as a constituent element is formed in such a manner as to coverthe surface of the center part 101.

The active material 100 including the center part 101 and the coveringpart 102 is thereby manufactured (Step S4). In a case of synthesizingthe active material (the center part 101 including the carbon-reducedsilicate glass), the composition or another factor of the silicate glassused as a raw material is so adjusted that the content of eachconstituent element with respect to all the constituent elementsexcluding oxygen, lithium, and carbon satisfies the condition describedabove. Specifically, the adjustment is so performed that the content ofsilicon is from 60 at % to 98 at % both inclusive, the content of thefirst element is from 1 at % to 25 at % both inclusive, the content ofthe second element is from 1 at % to 34 at % both inclusive, and thecontent of the third element is from 0 at % to 6 at % both inclusive inthe carbon-reduced silicate glass.

In the active material 100 (the center part 101) including thecarbon-reduced silicate glass manufactured by the carbon reductiontreatment, the physical property of the silicate glass has changed dueto the carbon reduction process. The two physical property conditionsrelating to XPS and Raman spectroscopy described above are thussatisfied.

According to the active material 100 and the method manufacturing theactive material 100 described above, the following action and effectsare obtained.

The active material 100 includes silicon, oxygen, the first element, thesecond element, and the third element as constituent elements, and thecontent of each constituent element with respect to all the constituentelements excluding oxygen and carbon satisfies the condition describedabove. In addition, the peak XA (the apex XAT and the shoulder XAS) isdetected as the result of analysis of the active material 100 measuredby XPS (the XPS spectrum of Si2p), and the peak RA (the apex RAT) isdetected as the result of analysis of the active material 100 measuredby Raman spectroscopy (the Raman spectrum).

In this case, unlike the case where the two physical property conditionsrelating to XPS and Raman spectroscopy are not satisfied, the reductionreaction of the silicate glass sufficiently proceeds, as describedabove. Accordingly, the crystallinity of the glass material includingSiO_(x) as a primary component is optimized. This makes it easy for theelectrode reactant to be sufficiently and stably inserted into orextracted from the active material 100, and also continuously makes iteasy for the electrode reactant to be inserted into or extracted fromthe active material 100 even if the electrode reaction is repeated. Itis therefore possible to obtain a superior battery characteristic in asecondary battery including the active material 100.

In particular, the half width of the peak XA may be 4.0 eV or greater.In this case, the center part 101 includes the carbon-reduced silicatecompound satisfying the two physical property conditions relating to XPSand Raman spectroscopy. Thus, it is possible to obtain a superiorbattery characteristic as described above. Further, the area ratio S2/S1may be 0.85 or greater in a case where the peak XA is decomposed intothe five Si-attributed peaks (the Si⁰ peak, the Si¹⁺ peak, the Si²⁺peak, the Si³⁺ peak, and the Si⁴⁺ peak). In this case, it is alsopossible to obtain a superior battery characteristic for a similarreason.

Further, the active material 100 may include the center part 101 and thecovering part 102. This allows the surface of the center part 101including the carbon-reduced silicate glass to be covered with thecovering part 102 having an electrically conductive property. Thisimproves the electrically conductive property of the active material 100as a whole. It is therefore possible to obtain a higher effect.

According to the method of manufacturing the active material 100, thesilicate glass including silicon, oxygen, the first element, the secondelement, and the third element as constituent elements is mixed with thecarbon source, following which the mixture of the silicate glass and thecarbon source is heated. Accordingly, the active material 100 issynthesized that includes the carbon-reduced silicate compound in whichthe content of each constituent element satisfies the conditiondescribed above and which satisfies the two physical property conditionsrelating to XPS and Raman spectroscopy. It is therefore possible toobtain the active material 100 that achieves a superior batterycharacteristic.

Moreover, to manufacture the active material 100 including SiO_(x) as aprimary component, only simple and inexpensive treatments including,without limitation, a mixing treatment and a heating treatment areneeded. This eliminates the need to perform a complicated and expensivetreatment such as codeposition of two vapor deposition sources (SiO₂ andSi). It is therefore possible to manufacture the active material 100easily and stably at low costs.

In particular, the carbon source may include the material such as acarbon material. This allows the silicate glass to be sufficientlyreduced in the carbon reduction treatment, and allows the covering part102 having a sufficient electrically conductive property to be formedeasily and stably. It is therefore possible to obtain a higher effect.

Next, a description is given of a secondary battery according to anembodiment of the technology, which is one application example of theactive material described above. Note that an electrode according to anembodiment of the technology is a part (one constituent element) of thesecondary battery, and is thus described below together.

A description is given below of a case where the active material 100 isused as a negative electrode active material, and is therefore used fora negative electrode.

The secondary battery described here is a secondary battery that obtainsa battery capacity by utilizing insertion and extraction of theelectrode reactant. The secondary battery includes a positive electrode,a negative electrode, and an electrolytic solution.

In the secondary battery, in order to prevent precipitation of theelectrode reactant on a surface of the negative electrode in the middleof charging, a charge capacity of the negative electrode is greater thana discharge capacity of the positive electrode. In other words, anelectrochemical capacity per unit area of the negative electrode is setto be greater than an electrochemical capacity per unit area of thepositive electrode.

In the following, a description is given of an example case where theelectrode reactant is lithium. A secondary battery utilizing insertionand extraction of lithium as the electrode reactant is a so-calledlithium-ion secondary battery.

First, a secondary battery of a laminated-film type is described. Thesecondary battery of the laminated-film type includes a film 20 havingsoftness or flexibility as an outer package member for containing abattery device.

FIG. 5 is a perspective view of a configuration of the secondary batteryof the laminated-film type. FIG. 6 illustrates a sectional configurationof a wound electrode body 10 illustrated in FIG. 5. FIG. 7 illustrates aplan configuration of each of a positive electrode 11 and a negativeelectrode 12 illustrated in FIG. 6.

Note that FIG. 5 illustrates a state in which the wound electrode body10 and the film 20 are separated away from each other. FIG. 6illustrates only a portion of the wound electrode body 10. FIG. 7illustrates a state in which the positive electrode 11 and the negativeelectrode 12 are separated away from each other.

As illustrated in FIG. 5, the secondary battery has the film 20 having apouch-shape in which a wound-type battery device (the wound electrodebody 10) is contained. A positive electrode lead 14 and a negativeelectrode lead 15 are coupled to the wound electrode body 10.

The film 20 is a single film member foldable in a direction of an arrowR (a dash-dot-dash line) illustrated in FIG. 5. The film 20 has adepression 20U. The depression 20U is a so-called deeply-drawn portiondesigned to contain the wound electrode body 10.

Specifically, the film 20 is a laminated film including three layers: afusion-bonding layer, a metal layer, and a surface protective layer thatare laminated in this order from an inner side. In a state where thefilm 20 is folded, outer edges of the fusion-bonding layer arefusion-bonded to each other. The fusion-bonding layer includes a polymercompound such as polypropylene. The metal layer includes a metalmaterial such as aluminum. The surface protective layer includes apolymer compound such as nylon. Note that the number of layers laminatedinto the film 20 is not limited to three. The film 20 may include onelayer, two layers, or four or more layers.

A sealing film 21 is interposed between the film 20 and the positiveelectrode lead 14, and a sealing film 22 is interposed between the film20 and the negative electrode lead 15. The sealing films 21 and 22 aremembers for preventing outside air from entering. The sealing films 21and 22 include, without limitation, one or more polyolefin resins havingadherence to the positive electrode lead 14 and the negative electrodelead 15, respectively. Examples of the polyolefin resin includepolyethylene, polypropylene, modified polyethylene, and modifiedpolypropylene. Note that the sealing film 21, the sealing film 22, orboth may be omitted.

As illustrated in FIGS. 5 and 6, the wound electrode body 10 includesthe positive electrode 11, the negative electrode 12, a separator 13,and an electrolytic solution. The electrolytic solution is a liquidelectrolyte. The wound electrode body 10 has a structure in which thepositive electrode 11 and the negative electrode 12 are stacked on eachother with the separator 13 interposed therebetween, and the stack ofthe positive electrode 11, the negative electrode 12, and the separator13 is wound.

The positive electrode 11, the negative electrode 12, and the separator13 are each impregnated with the electrolytic solution.

As illustrated in FIG. 6, the positive electrode 11 includes a positiveelectrode current collector 11A, and two positive electrode activematerial layers 11B provided on respective sides of the positiveelectrode current collector 11A. However, the positive electrode activematerial layer 11B may be provided on only one side of the positiveelectrode current collector 11A.

The positive electrode current collector 11A includes one or more ofelectrically conductive materials including, without limitation,aluminum, nickel, and stainless steel.

The positive electrode active material layer 11B includes one or more ofpositive electrode active materials into which lithium is inserted andfrom which lithium is extracted. The positive electrode active materiallayer 11B may further include a material such as a positive electrodebinder or a positive electrode conductor.

The positive electrode active material is not limited to a particularkind, and is a lithium-containing compound such as a lithium-containingtransition metal compound. The lithium-containing transition metalcompound includes lithium and one or more of transition metal elements,and may further include one or more of other elements. The otherelements may be any elements other than a transition metal element, andare not limited to particular kinds. In particular, the other elementsare preferably those belonging to Groups 2 to 15 in the long periodperiodic table. Note that the lithium-containing transition metalcompound may be an oxide, or may be, for example, one of a phosphoricacid compound, a silicic acid compound, and a boric acid compound.

Specific examples of the oxide include LiNiO₂, LiCoO₂,LiCo_(0.98)Al_(0.01)Mg_(0.33)O₂, LiNi_(0.5)Co_(0.2)Mn_(0.302),LiNi_(0.8)Co_(0.15)Al_(0.05)O₂, LiNi_(0.33)Co_(0.33)Mn_(0.33)O₂,Li_(1.2)Mn_(0.52)Co_(0.175)Ni_(0.1)O₂,Li_(1.15)(Mn_(0.65)Ni_(0.22)Co_(0.13))O₂, and LiMn₂O₄. Specific examplesof the phosphoric acid compound include LiFePO₄, LiMnPO₄,LiFe_(0.5)Mn_(0.5)PO₄, and LiFe_(0.3)Mn_(0.7)PO₄.

The positive electrode binder includes one or more of materialsincluding, without limitation, a synthetic rubber and a polymercompound. Examples of the synthetic rubber include astyrene-butadiene-based rubber, a fluorine-based rubber, and ethylenepropylene diene. Examples of the polymer compound include polyvinylidenedifluoride, polyimide, and carboxymethyl cellulose.

The positive electrode conductor includes one or more of electricallyconductive materials including, without limitation, a carbon material.Examples of the carbon material include graphite, carbon black,acetylene black, and Ketjen black. The positive electrode conductor maybe a material such as a metal material or an electrically conductivepolymer as long as the material has an electrically conductive property.

The positive electrode active material layer 11B is provided on aportion of the positive electrode current collector 11A on both sides ofthe positive electrode current collector 11A. Accordingly, a portion ofthe positive electrode current collector 11A on which the positiveelectrode active material layer 11B is not provided is exposed withoutbeing covered with the positive electrode active material layer 11B.

Specifically, the positive electrode current collector 11A extends in alongitudinal direction (X-axis direction) as illustrated in FIG. 7, andincludes a covered portion 11AX and paired uncovered portions 11AY. Thecovered portion 11AX is a portion which are located at the middleportion of the positive electrode current collector 11A in thelongitudinal direction and on which the positive electrode activematerial layer 11B is formed. The paired uncovered portions 11AY areportions which are located at respective ends of the positive electrodecurrent collector 11A in the longitudinal direction and on which thepositive electrode active material layer 11B is not formed. Accordingly,the covered portion 11AX is covered with the positive electrode activematerial layer 11B, whereas the paired uncovered portions 11AY areexposed without being covered with the positive electrode activematerial layer 11B. In FIG. 7, the positive electrode active materiallayer 11B is slightly shaded.

As illustrated in FIG. 6, the negative electrode 12 includes a negativeelectrode current collector 12A, and two negative electrode activematerial layers 12B provided on respective sides of the negativeelectrode current collector 12A. However, the negative electrode activematerial layer 12B may be provided only on one side of the negativeelectrode current collector 12A.

The negative electrode current collector 12A includes one or more ofelectrically conductive materials including, without limitation, copper,aluminum, nickel, and stainless steel.

The negative electrode active material layer 12B includes one or more ofnegative electrode active materials into which lithium is inserted andfrom which lithium is extracted. The negative electrode active materiallayer 12B may further include a material such as a negative electrodebinder or a negative electrode conductor. Details of each of thenegative electrode binder and the negative electrode conductor aresimilar to details of each of the positive electrode binder and thepositive electrode conductor described above.

The negative electrode active material has a configuration similar tothat of the active material 100 described above. However, the negativeelectrode active material may further include one or more othermaterials. Examples of the other materials include a carbon material anda metal-based material. Examples of the carbon material includegraphitizable carbon, non-graphitizable carbon, and graphite. Themetal-based material is a metal element or a metalloid element that isable to form an alloy with lithium. More specifically, the metal-basedmaterial is, for example, silicon or tin. The metal-based material maybe a simple substance, an alloy, a compound, or a mixture of two or morethereof. The carbon-reduced silicate glass described above is excludedfrom the examples of the metal-based material described here.

Specific examples of the metal-based material include SiB₄, SiB₆, Mg₂Si,Ni₂Si, TiSi₂, MoSi₂, CoSi₂, NiSi₂, CaSi₂, CrSi₂, Cu₅Si, FeSi₂, MnSi₂,NbSi₂, TaSi₂, VSi₂, WSi₂, ZnSi₂, SiC, Si₃N₄, Si₂N₂O, SiO_(v) (0<v≤2 or0.2<v<1.4), LiSiO, SnO_(w) (0<w≤2), SnSiO₃, LiSnO, and Mg₂Sn.

A method of forming the negative electrode active material layer 12B isnot limited to a particular method, and includes one or more of methodsincluding, without limitation, a coating method, a vapor-phase method, aliquid-phase method, a thermal spraying method, and a firing (sintering)method.

The negative electrode active material layer 12B is provided on theentire negative electrode current collector 12A on both sides of thenegative electrode current collector 12A. Accordingly, the negativeelectrode current collector 12A is entirely covered with the negativeelectrode active material layer 12B without being exposed.

Specifically, as illustrated in FIG. 7, the negative electrode currentcollector 12A extends in the longitudinal direction (X-axis direction),and the negative electrode active material layer 12B includes pairednon-opposed portions 12BZ. The paired non-opposed portions 12BZ areopposed to the paired uncovered portions 11AY. That is, the pairednon-opposed portions 12BZ are not opposed to the positive electrodeactive material layer 11B and thus do not contribute to charging anddischarging reactions. In FIG. 7, the negative electrode active materiallayer 12B is darkly shaded.

The negative electrode active material layer 12B is entirely provided oneach of both sides of the negative electrode current collector 12A,whereas the positive electrode active material layer 11B is provided ononly a portion (the covered portion 11AX) of each of both sides of thepositive electrode current collector 11A, in order to prevent lithiumextracted from the positive electrode active material layer 11B at thetime of charging from precipitating on the surface of the negativeelectrode 12.

In a case of examining whether the two physical property conditionsrelating to XPS and Raman spectroscopy described above are satisfied expost facto, i.e., after the completion of the secondary battery orduring use of the secondary battery, it is preferable to use thenon-opposed portions 12BZ as the negative electrode active materiallayer 12B for collecting the negative electrode active material foranalysis. A reason for this is that the non-opposed portions 12BZ hardlycontribute to the charging and discharging reactions, and the state(e.g., the composition and the physical property) of the negativeelectrode active material (carbon-reduced silicate glass) is thus easilymaintained as the state at the time of forming the negative electrode 12without being influenced by the charging and discharging reactions.Accordingly, it is possible to examine whether the two physical propertyconditions are satisfied in a highly stable and reproducible manner evenin a case where the secondary battery has been used.

As illustrated in FIG. 6, the separator 13 is interposed between thepositive electrode 11 and the negative electrode 12. The separator 13 isan insulating porous film that allows lithium to pass therethrough whilepreventing contact (short circuiting) between the positive electrode 11and the negative electrode 12. The separator 13 may be a single-layerfilm including one porous film, or may be a multi-layer film includingtwo or more porous films that are stacked on each other. The porous filmincludes one or more of polymer compounds including, without limitation,polytetrafluoroethylene, polypropylene, and polyethylene.

The electrolytic solution includes a solvent and an electrolyte salt.Only one solvent may be used, or two or more solvents may be used. Inaddition, only one electrolyte salt may be used, or two or moreelectrolyte salts may be used.

The solvent includes a non-aqueous solvent (an organic solvent), and theelectrolytic solution including the non-aqueous solvent is a so-callednon-aqueous electrolytic solution.

Examples of the non-aqueous solvent include esters and ethers. Morespecifically, examples of the non-aqueous solvent include acarbonic-acid-ester-based compound, a carboxylic-ester-based compound,and a lactone-based compound.

Examples of the carbonic-acid-ester-based compound include a cycliccarbonic acid ester and a chain carbonic acid ester. Examples of thecyclic carbonic acid ester include ethylene carbonate and propylenecarbonate. Examples of the chain carbonic acid ester include dimethylcarbonate, diethyl carbonate, and methyl ethyl carbonate. Examples ofthe carboxylic-ester-based compound include ethyl acetate, ethylpropionate, and ethyl trimethylacetate. Examples of the lactone-basedcompound include γ-butyrolactone and γ-valerolactone. Examples of theethers other than the lactone-based compounds described above include1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, and 1,4-dioxane.

Examples of the non-aqueous solvent further include an unsaturatedcyclic carbonic acid ester, a halogenated carbonic acid ester, asulfonic acid ester, a phosphoric acid ester, an acid anhydride, anitrile compound, and an isocyanate compound. A reason for this is thatchemical stability of the electrolytic solution improves.

Specific examples of the unsaturated cyclic carbonic acid ester includevinylene carbonate, vinylethylene carbonate, and methylene ethylenecarbonate. Examples of the halogenated carbonic acid ester includefluoroethylene carbonate and difluoroethylene carbonate. Examples of thesulfonic acid ester include 1,3-propane sultone. Examples of thephosphoric acid ester include trimethyl phosphate. Examples of the acidanhydride include a cyclic carboxylic acid anhydride, a cyclicdisulfonic acid anhydride, and a cyclic carboxylic acid sulfonic acidanhydride. Examples of the cyclic carboxylic acid anhydride includesuccinic anhydride, glutaric anhydride, and maleic anhydride. Examplesof the cyclic disulfonic acid anhydride include ethane disulfonicanhydride and propane disulfonic anhydride. Examples of the cycliccarboxylic acid sulfonic acid anhydride include sulfobenzoic anhydride,sulfopropionic anhydride, and sulfobutyric anhydride. Examples of thenitrile compound include acetonitrile and succinonitrile. Examples ofthe isocyanate compound include hexamethylene diisocyanate.

The electrolyte salt includes one or more of light metal saltsincluding, without limitation, a lithium salt. Examples of the lithiumsalt include lithium hexafluorophosphate (LiPF₆), lithiumtetrafluoroborate (LiBF₄), lithium trifluoromethanesulfonate (LiCF₃SO₃),lithium bis(fluorosulfonyl)imide (LiN(FSO₂)₂), lithiumbis(trifluoromethanesulfonyl)imide (LiN(CF₃SO₂)₂), lithiumtris(trifluoromethanesulfonyl)methide (LiC(CF₃SO₂)₃), and lithiumbis(oxalato)borate (LiB(C₂O₄)₂). The content of the electrolyte salt isnot limited to a particular content; however, the content is from 0.3mol/kg to 3.0 mol/kg both inclusive with respect to the solvent. Areason for this is that high ion conductivity is obtainable.

The positive electrode lead 14 is coupled to the positive electrode 11(the positive electrode current collector 11A), and the negativeelectrode lead 15 is coupled to the negative electrode 12 (the negativeelectrode current collector 12A). The positive electrode lead 14 and thenegative electrode lead 15 are each extracted from inside the film 20 tooutside in a similar direction. The positive electrode lead 14 includesone or more of electrically conductive materials including, withoutlimitation, aluminum, and the negative electrode lead 15 includes one ormore of electrically conductive materials including, without limitation,copper, nickel, and stainless steel. The positive electrode lead 14 andthe negative electrode lead 15 each have a shape such as a thin plateshape or a meshed shape.

The secondary battery operates as follows. Upon charging the secondarybattery, lithium is extracted from the positive electrode 11, and theextracted lithium is inserted into the negative electrode 12 via theelectrolytic solution. In contrast, upon discharging the secondarybattery, lithium is extracted from the negative electrode 12, and theextracted lithium is inserted into the positive electrode 11 via theelectrolytic solution. Upon charging and discharging the secondarybattery, lithium is inserted and extracted in an ionic state.

In a case of manufacturing the secondary battery, the positive electrode11 and the negative electrode 12 are fabricated and the electrolyticsolution is prepared, following which the secondary battery is assembledaccording to a procedure described below.

First, the positive electrode active material is mixed with, on anas-needed basis, a material such as the positive electrode binder or thepositive electrode conductor to thereby obtain a positive electrodemixture. Thereafter, the positive electrode mixture is put into asolvent such as an organic solvent to thereby prepare a positiveelectrode mixture slurry in a paste state. Lastly, the positiveelectrode mixture slurry is applied on each of both sides of thepositive electrode current collector 11A to thereby form the positiveelectrode active material layer 11B. Thereafter, the positive electrodeactive material layer 11B may be compression-molded using a rollpressing machine. In this case, the positive electrode active materiallayer 11B may be heated. The positive electrode active material layer11B may be compression-molded multiple times. The positive electrodeactive material layer 11B is thus formed on each of both sides of thepositive electrode current collector 11A. As a result, the positiveelectrode 11 is fabricated.

The negative electrode active material layer 12B is formed on each ofboth sides of the negative electrode current collector 12A by aprocedure similar to the fabrication procedure of the positive electrode11 described above. Specifically, the negative electrode active materialis mixed with, on an as-needed basis, a material such as the negativeelectrode binder or the negative electrode conductor to thereby obtain anegative electrode mixture. Thereafter, the negative electrode mixtureis put into a solvent such as an organic solvent to thereby prepare anegative electrode mixture slurry in a paste state. Thereafter, thenegative electrode mixture slurry is applied on each of both sides ofthe negative electrode current collector 12A to thereby form thenegative electrode active material layer 12B. Thereafter, the negativeelectrode active material layer 12B may be compression-molded. Thenegative electrode active material layer 12B is thus formed on each ofboth sides of the negative electrode current collector 12A. As a result,the negative electrode 12 is fabricated.

The electrolyte salt is put into the solvent such as an organic solvent.This allows the electrolyte salt to be dispersed or dissolved into thesolvent. As a result, the electrolytic solution is prepared.

First, the positive electrode lead 14 is coupled to the positiveelectrode 11 (the positive electrode current collector 11A) by a methodsuch as a welding method, and the negative electrode lead 15 is coupledto the negative electrode 12 (the negative electrode current collector12A) by a method such as a welding method. Thereafter, the positiveelectrode 11 and the negative electrode 12 are stacked on each otherwith the separator 13 interposed therebetween, following which the stackof the positive electrode 11, the negative electrode 12, and theseparator 13 is wound to thereby fabricate a wound body. Thereafter, thewound body is contained inside the depression 20U and the film 20 isfolded, following which outer edges of two sides of the film 20 (thefusion-bonding layer) are bonded to each other by a method such as athermal fusion bonding method. Thus, the wound body is placed into thefilm 20 having the pouch shape. Lastly, the electrolytic solution isinjected into the film 20 having the pouch shape, following which theouter edges of the remaining one side of the film 20 (the fusion-bondinglayer) are bonded with each other using a method such as a thermalfusion bonding method. In this case, the sealing film 21 is disposedbetween the film 20 and the positive electrode lead 14, and the sealingfilm 22 is disposed between the film 20 and the negative electrode lead15. The wound body is thereby impregnated with the electrolyticsolution. Thus, the wound electrode body 10 is fabricated. Accordingly,the wound electrode body 10 is sealed in the film 20 having the pouchshape. As a result, the secondary battery of the laminated-film type iscompleted.

According to the secondary battery of the laminated-film type, thenegative electrode active material included in the negative electrode 12has a configuration similar to that of the active material 100. Thismakes it easy for lithium to be sufficiently and stably inserted into orextracted from the negative electrode active material, and alsocontinuously makes it easy for lithium to be inserted into or extractedfrom the negative electrode active material even if the charging anddischarging reactions are repeated, for a reason similar to thatdescribed above in relation to the active material 100. It is thereforepossible to obtain a superior battery characteristic.

Other action and effects of the secondary battery of the laminated-filmtype and the manufacturing method thereof are similar to the otheraction and effects of the active material 100 and the manufacturingmethod thereof.

Next, a description is given of the secondary battery of a cylindricaltype including a battery can 41 with stiffness as an outer packagemember for containing a battery device inside.

FIG. 8 illustrates a sectional configuration of the secondary battery ofthe cylindrical type. In the following description, reference will bemade as necessary to the components of the secondary battery of thelaminated-film type, which have been already described above, and FIG.6.

As illustrated in FIG. 8, the secondary battery includes a pair ofinsulating plates 42 and 43 and a battery device of a wound type (awound electrode body 30) that are provided inside the battery can 41having a cylindrical shape. A positive electrode lead 34 and a negativeelectrode lead 35 are coupled to the wound electrode body 30.

The battery can 41 has a hollow structure with a closed end and an openend, and includes one or more of metal materials including, withoutlimitation, iron, aluminum, and an alloy thereof. The battery can 41 hasa surface that may be plated with, for example, a metal material such asnickel. The insulating plates 42 and 43 are disposed in such a manner asto sandwich the wound electrode body 30 therebetween, and extend in adirection intersecting a wound peripheral surface of the wound electrodebody 30.

A battery cover 44, a safety valve mechanism 45, and a positivetemperature coefficient device (PTC device) 46 are crimped at the openend of the battery can 41 by means of a gasket 47 having an insulatingproperty, thereby sealing the open end of the battery can 41. Thebattery cover 44 includes a material similar to a material included inthe battery can 41. The safety valve mechanism 45 and the PTC device 46are each disposed on an inner side of the battery cover 44. The safetyvalve mechanism 45 is electrically coupled to the battery cover 44 viathe PTC device 46. When an internal pressure of the battery can 41reaches a certain level or higher as a result of causes including,without limitation, internal short circuiting and heating from outside,a disk plate 45A inverts, thereby cutting off the electrical couplingbetween the battery cover 44 and the wound electrode body 30. The PTCdevice 46 involves an increase in resistance in accordance with a risein temperature, in order to prevent abnormal heat generation resultingfrom a large current. The gasket 47 may have a surface on which amaterial such as asphalt is applied, for example.

The wound electrode body 30 includes a positive electrode 31, a negativeelectrode 32, a separator 33, and an electrolytic solution. The woundelectrode body 30 has a structure in which the positive electrode 31 andthe negative electrode 32 are stacked on each other with the separator33 interposed therebetween, and the stack of the positive electrode 31,the negative electrode 32, and the separator 33 is wound. The positiveelectrode 31, the negative electrode 32, and the separator 33 are eachimpregnated with the electrolytic solution. The positive electrode lead34 is coupled to the positive electrode 31 (a positive electrode currentcollector 31A), and the negative electrode lead 35 is coupled to thenegative electrode 32 (a negative electrode current collector 32A).

A center pin 36 is disposed in a space provided at the winding center ofthe wound electrode body 30. Note, however, that the center pin 36 maybe omitted. The positive electrode lead 34 includes one or more ofelectrically conductive materials including, without limitation,aluminum. The positive electrode lead 34 is electrically coupled to thebattery cover 44 via the safety valve mechanism 45. The negativeelectrode lead 35 includes one or more of electrically conductivematerials including, without limitation, copper, nickel, and stainlesssteel (SUS). The negative electrode lead 35 is electrically coupled tothe battery can 41. The positive electrode lead 34 and the negativeelectrode lead 35 each have a shape such as a thin plate shape or ameshed shape.

As illustrated in FIG. 6, the positive electrode 31 includes thepositive electrode current collector 31A and a positive electrode activematerial layer 31B, and the negative electrode 32 includes the negativeelectrode current collector 32A and a negative electrode active materiallayer 32B. The positive electrode current collector 31A, the positiveelectrode active material layer 31B, the negative electrode currentcollector 32A, and the negative electrode active material layer 32B haveconfigurations similar to the configurations of the positive electrodecurrent collector 11A, the positive electrode active material layer 11B,the negative electrode current collector 12A, and the negative electrodeactive material layer 12B, respectively. The separator 33 has aconfiguration similar to the configuration of the separator 13.

The secondary battery operates as follows. Upon charging the secondarybattery, lithium is extracted from the positive electrode 31, and theextracted lithium is inserted into the negative electrode 32 via theelectrolytic solution. In contrast, upon discharging the secondarybattery, lithium is extracted from the negative electrode 32, and theextracted lithium is inserted into the positive electrode 31 via theelectrolytic solution. Upon charging and discharging the secondarybattery, lithium is inserted and extracted in an ionic state.

In a case of manufacturing the secondary battery, the positive electrode31 and the negative electrode 32 are fabricated, following which thesecondary battery is assembled according to a procedure described below.Note that the description of the procedure for preparing theelectrolytic solution, which has been already given above, is omittedhere.

The positive electrode 31 is fabricated through a procedure similar tothe procedure for fabricating the positive electrode 11, and thenegative electrode 32 is fabricated through a procedure similar to theprocedure for fabricating the negative electrode 12. That is, in a caseof fabricating the positive electrode 31, the positive electrode activematerial layer 31B is formed on each of both sides of the positiveelectrode current collector 31A. In a case of fabricating the negativeelectrode 32, the negative electrode active material layer 32B is formedon each of both sides of the negative electrode current collector 32A.

First, the positive electrode lead 34 is coupled to the positiveelectrode 31 (the positive electrode current collector 31A) by a methodsuch as a welding method, and the negative electrode lead 35 is coupledto the negative electrode 32 (the negative electrode current collector32A) by a method such as welding method. Thereafter, the positiveelectrode 31 and the negative electrode 32 are stacked on each otherwith the separator 33 interposed therebetween, following which the stackof the positive electrode 31, the negative electrode 32, and theseparator 33 is wound to thereby fabricate a wound body. Thereafter, thecenter pin 36 is disposed in the space provided at the winding center ofthe wound body.

Thereafter, the wound body is interposed between the pair of insulatingplates 42 and 43, and the wound body in that state is contained in thebattery can 41 together with the insulating plates 42 and 43. In thiscase, the positive electrode lead 34 is coupled to the safety valvemechanism 45 by a method such as a welding method, and the negativeelectrode lead 35 is coupled to the battery can 41 by a method such as awelding method. Thereafter, the electrolytic solution is injected intothe battery can 41 to thereby impregnate each of the positive electrode31, the negative electrode 32, and the separator 33 with theelectrolytic solution. As a result, the wound electrode body 30 isfabricated.

Lastly, the open end of the battery can 41 is crimped by means of thegasket 47 to thereby attach the battery cover 44, the safety valvemechanism 45, and the PTC device 46 to the open end of the battery can41. Thus, the wound electrode body 30 is sealed in the battery can 41.As a result, the secondary battery of the cylindrical type is completed.

According to the secondary battery of the cylindrical type, the negativeelectrode active material included in the negative electrode 32 has aconfiguration similar to that of the active material 100. This makes itpossible for the secondary battery of the cylindrical type to provide asuperior battery characteristic for a reason similar to that describedabove in relation to the secondary battery of the laminated-film type.

Other action and effects of the secondary battery of the cylindricaltype are similar to the other action and effects of the secondarybattery of the laminated-film type.

Next, a description is given of modifications of the active material andthe secondary battery described above. The configuration of each of theactive material and the secondary battery may be changed as appropriateas described below. However, any two or more of the modificationsdescribed in sequence below may be combined to each other.

[Modification 1]

The active material 100 illustrated in FIG. 1 includes the center part101 and the covering part 102. However, the active material 100 mayinclude only the center part 101 and may not include the covering part102. In this case, the covering part 102 may be removed after the activematerial 100 including the center part 101 and the covering part 102 ismanufactured. Similar effects are obtainable also in this case as theelectrode reactant is insertable into and extractable from the activematerial 100 (the center part 101).

However, to improve the electrically conductive property of the activematerial 100 as a whole, the active material 100 preferably includesboth the center part 101 and the covering part 102 as described above.

[Modification 2]

The battery device of the wound type (the wound electrode body 10) isused in FIGS. 5 and 6. However, a battery device of a stacked type (astacked electrode body 50) may be used instead of the wound electrodebody 10, as illustrated in FIG. 9 corresponding to FIG. 5, and FIG. 10corresponding to FIG. 6.

The secondary battery of the laminated-film type illustrated in FIGS. 9and 10 has a configuration similar to that of the secondary battery ofthe laminated-film type illustrated in FIGS. 5 and 6 except that thestacked electrode body 50 (the positive electrode 51, the negativeelectrode 52, and the separator 53), the positive electrode lead 54, andthe negative electrode lead 55 are included instead of the woundelectrode body 10 (the positive electrode 11, the negative electrode 12,and the separator 13), the positive electrode lead 14, and the negativeelectrode lead 15.

The positive electrode 51, the negative electrode 52, the separator 53,the positive electrode lead 54, and the negative electrode lead 55 haveconfigurations similar to the configurations of the positive electrode11, the negative electrode 12, the separator 13, the positive electrodelead 14, and the negative electrode lead 15, respectively, except thefollowing points.

In the stacked electrode body 50, the positive electrode 51 and thenegative electrode 52 are alternately stacked on each other with theseparator 53 interposed therebetween. The number of the positiveelectrodes 51, the negative electrodes 52, and the separators 53 to bestacked are not limited to a particular number. Here, the multiplepositive electrodes 51 and the multiple negative electrodes 52 arealternately stacked on each other with the multiple separators 53interposed therebetween. The positive electrodes 51, the negativeelectrodes 52, and the separators 53 are each impregnated with theelectrolytic solution having the configuration described above. Thepositive electrode 51 includes a positive electrode current collector51A and a positive electrode active material layer 51B. The negativeelectrode 52 includes a negative electrode current collector 52A and anegative electrode active material layer 52B.

As illustrated in FIGS. 9 and 10, the positive electrode currentcollector 51A includes a projecting part 51AT on which the positiveelectrode active material layer 51B is not formed, and the negativeelectrode current collector 52A includes a projecting part 52AT on whichthe negative electrode active material layer 52B is not formed. Theprojecting part 52AT is disposed at a position not overlapping theprojecting part 51AT. Two or more projecting parts 51AT are joined toeach other to form a single joint part 51Z having a lead shape. The twoor more projecting parts 52AT are joined to each other to form a singlejoint part 52Z having a lead shape. The positive electrode lead 54 iscoupled to the joint part 51Z, and the negative electrode lead 55 iscoupled to the joint part 52Z.

A manufacturing method of the secondary battery of the laminated-filmtype illustrated in FIGS. 9 and 10 is similar to the manufacturingmethod of the secondary battery of the laminated-film type illustratedin FIGS. 5 and 6 except that the stacked electrode body 50 (the positiveelectrode lead 54 and the negative electrode lead 55) is fabricatedinstead of the wound electrode body 10 (the positive electrode lead 14and the negative electrode lead 15).

In a case of fabricating the stacked electrode body 50, first, thepositive electrode 51 including the positive electrode active materiallayer 51B formed on each of both sides of the positive electrode currentcollector 51A (except the projecting part 51AT) and the negativeelectrode 52 including the negative electrode active material layer 52Bformed on each of both sides of the negative electrode current collector52A (except the projecting part 52AT) are fabricated, following whichthe multiple positive electrodes 51 and the multiple negative electrodes52 are alternately stacked on each other with the plurality ofseparators 53 interposed therebetween to thereby form a stacked body.Thereafter, the two or more projecting parts 51AT are joined to eachother by a method such as a welding method to form the joint part 51Z,and the two or more projecting parts 52AT are joined to each other by amethod such as a welding method to form the joint part 52Z. Thereafter,the positive electrode lead 54 is coupled to the projecting part 51AT bya method such as a welding method, and the negative electrode lead 55 iscoupled to the projecting part 52AT by a method such as a weldingmethod. Lastly, the electrolytic solution is injected into the film 20having the pouch shape in which the stacked body is contained, followingwhich the film 20 is sealed. Thus, the stacked body is impregnated withthe electrolytic solution. As a result, the stacked electrode body 50 isfabricated.

In a case where the stacked electrode body 50 is used, it is alsopossible to obtain effects similar to the effects obtained in a casewhere the wound electrode body 10 is used. Although not specificallyillustrated here, the battery device of the stacked type (the stackedelectrode body 50) may be applied to the secondary battery of thecylindrical type illustrated in FIGS. 6 and 8.

[Modification 3]

The number of the positive electrode leads 54 and the number of thenegative electrode leads 55 in the secondary battery of thelaminated-film type illustrated in FIGS. 9 and 10 are each not limitedto a particular number. That is, the number of the positive electrodeleads 54 is not limited to one and may be two or greater. The number ofthe negative electrode lead 55 is not limited to one and may be two orgreater. Similar effects are obtainable also in the case where thenumber of the positive electrode leads 54 and the number of the negativeelectrode leads 55 are changed. Although not specifically illustratedhere, the number of the positive electrode leads 34 and the number ofthe negative electrode leads 35 may be changed in the secondary batteryof the cylindrical type illustrated in FIGS. 6 and 8.

[Modification 4]

The separator 13 which is a porous film is used in the secondary batteryof the laminated-film type illustrated in FIGS. 5 and 6. However,although not specifically illustrated here, a separator of a stackedtype which includes a polymer compound layer may be used instead of theseparator 13 which is the porous film.

Specifically, the separator of the stacked type includes a base layerwhich is the porous film described above, and a polymer compound layerprovided on one or both sides of the base layer. A reason for this isthat adherence of the separator to each of the positive electrode 11 andthe negative electrode 12 is improved, which helps to prevent occurrenceof a positional displacement of the wound electrode body 10. This helpsto prevent swelling of the secondary battery, for example, even when thedecomposition reaction of the electrolytic solution occurs. The polymercompound layer includes a polymer compound such as polyvinylidenedifluoride. A reason for this is that polyvinylidene difluoride has ahigh physical strength and is electrochemically stable.

The base layer, the polymer compound layer, or both may include one ormore of a plurality of kinds of particles including, without limitation,inorganic particles and resin particles. A reason for this is thatmaterials, for example, the particles dissipate heat when the secondarybattery generates heat, thereby improving the thermal resistance andsafety of the secondary battery. The inorganic particles are not limitedto a particular kind. Examples of the inorganic particles includeparticles of aluminum oxide (alumina), aluminum nitride, boehmite,silicon oxide (silica), titanium oxide (titania), magnesium oxide(magnesia), and zirconium oxide (zirconia).

In a case of fabricating the separator of the stacked type, a precursorsolution including, without limitation, a polymer compound and anorganic solvent is prepared, following which the precursor solution isapplied on one or both sides of the base layer.

Similar effects are obtainable also in the case where the separator ofthe stacked type is used, as lithium is movable between the positiveelectrode 11 and the negative electrode 12. Note that the separator ofthe stacked type may be applied to the secondary battery of thecylindrical type illustrated in FIGS. 5 and 6.

[Modification 5]

In the secondary battery of the laminated-film type illustrated in FIGS.5 and 6, the electrolytic solution, which is a liquid electrolyte, isused. However, although not specifically illustrated here, anelectrolyte layer which is a gel electrolyte may be used instead of theelectrolytic solution.

In the wound electrode body 10 including the electrolyte layer, thepositive electrode 11 and the negative electrode 12 are stacked on eachother with the separator 13 and the electrolyte layer interposedtherebetween, following which the stack of the positive electrode 11,the negative electrode 12, the separator 13, and the electrolyte layeris wound. The electrolyte layer is interposed between the positiveelectrode 11 and the separator 13, and between the negative electrode 12and the separator 13.

Specifically, the electrolyte layer includes a polymer compound togetherwith the electrolytic solution. The electrolytic solution is held by thepolymer compound in the electrolyte layer. The configuration of theelectrolytic solution is as described above. The polymer compoundincludes, for example, polyvinylidene difluoride. In a case of formingthe electrolyte layer, a precursor solution that includes materialsincluding, without limitation, the electrolytic solution, the polymercompound, and an organic solvent is prepared, following which theprecursor solution is applied on each of both sides of the positiveelectrode 11 and each of both sides of the negative electrode 12.

Similar effects are obtainable also in the case where the electrolytelayer is used, as lithium is movable between the positive electrode 11and the negative electrode 12 via the electrolyte layer. Note that theelectrolyte layer may be applied to the secondary battery of thecylindrical type illustrated in FIGS. 6 and 8.

Next, a description is given of applications (application examples) ofthe above-described secondary battery.

The applications of the secondary battery are not particularly limitedas long as they are, for example, machines, equipment, instruments,apparatuses, or systems (an assembly of a plurality of pieces ofequipment, for example) in which the secondary battery is usable mainlyas a driving power source, an electric power storage source for electricpower accumulation, or any other source. The secondary battery used as apower source may serve as a main power source or an auxiliary powersource. The main power source is preferentially used regardless of thepresence of any other power source. The auxiliary power source may beused in place of the main power source, or may be switched from the mainpower source on an as-needed basis. In a case where the secondarybattery is used as the auxiliary power source, the kind of the mainpower source is not limited to the secondary battery.

Specific examples of the applications of the secondary battery include:electronic equipment including portable electronic equipment; portablelife appliances; apparatuses for data storage; electric power tools;battery packs to be mounted as detachable power sources on, for example,laptop personal computers; medical electronic equipment; electricvehicles; and electric power storage systems. Examples of the electronicequipment include video cameras, digital still cameras, mobile phones,laptop personal computers, cordless phones, headphone stereos, portableradios, portable televisions, and portable information terminals.Examples of the portable life appliances include electric shavers.Examples of the apparatuses for data storage include backup powersources and memory cards. Examples of the electric power tools includeelectric drills and electric saws. Examples of the medical electronicequipment include pacemakers and hearing aids. Examples of the electricvehicles include electric automobiles including hybrid automobiles.Examples of the electric power storage systems include home batterysystems for accumulation of electric power for a situation such asemergency. Note that the secondary battery may have a battery structureof the above-described laminated-film type, a cylindrical type, or anyother type. Further, multiple secondary batteries may be used, forexample, as a battery pack or a battery module.

In particular, the battery pack and the battery module are eacheffectively applied to relatively large-sized equipment, etc., includingan electric vehicle, an electric power storage system, and an electricpower tool. The battery pack, as will be described later, may include asingle battery, or may include an assembled battery. The electricvehicle is a vehicle that operates (travels) using the secondary batteryas a driving power source, and may be an automobile that is additionallyprovided with a driving source other than the secondary battery asdescribed above, such as a hybrid automobile. The electric power storagesystem is a system that uses the secondary battery as an electric powerstorage source. An electric power storage system for home useaccumulates electric power in the secondary battery which is an electricpower storage source, and the accumulated electric power may thus beutilized for using, for example, home appliances.

Some application examples of the secondary battery will now be describedin detail. The configurations of the application examples describedbelow are merely examples, and are appropriately modifiable. Thesecondary battery used in the following application examples is notlimited to a particular type, and may be the laminated-film type or thecylindrical type.

FIG. 11 illustrates a block configuration of a battery pack including asingle battery. The battery pack described here is a simple battery pack(a so-called soft pack) including one secondary battery, and is to bemounted on, for example, electronic equipment typified by a smartphone.

As illustrated in FIG. 11, the battery pack includes an electric powersource 61 and a circuit board 62. The circuit board 62 is coupled to theelectric power source 61, and includes a positive electrode terminal 63,a negative electrode terminal 64, and a temperature detection terminal(a so-called T terminal) 65.

The electric power source 61 includes one secondary battery. Thesecondary battery has a positive electrode lead coupled to the positiveelectrode terminal 63 and a negative electrode lead coupled to thenegative electrode terminal 64. The electric power source 61 iscouplable to outside via the positive electrode terminal 63 and thenegative electrode terminal 64, and is thus chargeable and dischargeablevia the positive electrode terminal 63 and the negative electrodeterminal 64. The circuit board 62 includes a controller 66, a switch 67,a PTC device 68, and a temperature detector 69. However, the PTC device68 may be omitted.

The controller 66 includes, for example, a central processing unit (CPU)and a memory, and controls an overall operation of the battery pack. Thecontroller 66 detects and controls a use state of the electric powersource 61 on an as-needed basis.

If a battery voltage of the electric power source 61 (the secondarybattery) reaches an overcharge detection voltage or an overdischargedetection voltage, the controller 66 turns off the switch 67. Thisprevents a charging current from flowing into a current path of theelectric power source 61. In addition, if a large current flows uponcharging or discharging, the controller 66 turns off the switch 67 toblock the charging current. The overcharge detection voltage and theoverdischarge detection voltage are not particularly limited. Forexample, the overcharge detection voltage is 4.2 V±0.05 V and theoverdischarge detection voltage is 2.4 V±0.1 V.

The switch 67 includes, for example, a charge control switch, adischarge control switch, a charging diode, and a discharging diode. Theswitch 67 performs switching between coupling and decoupling between theelectric power source 61 and external equipment in accordance with aninstruction from the controller 66. The switch 67 includes, for example,a metal-oxide-semiconductor field-effect transistor (MOSFET) including ametal-oxide semiconductor. The charging and discharging currents aredetected on the basis of an ON-resistance of the switch 67.

The temperature detector 69 includes a temperature detection device suchas a thermistor. The temperature detector 69 measures a temperature ofthe electric power source 61 using the temperature detection terminal65, and outputs a result of the temperature measurement to thecontroller 66. The result of the temperature measurement to be obtainedby the temperature detector 69 is used, for example, in a case where thecontroller 66 performs charge/discharge control upon abnormal heatgeneration or in a case where the controller 66 performs a correctionprocess upon calculating a remaining capacity.

FIG. 12 illustrates a block configuration of a battery pack including anassembled battery. In the following description, reference will be madeas necessary to the components of the battery pack including the singlebattery (FIG. 11).

As illustrated in FIG. 12, the battery pack includes a positiveelectrode terminal 81 and a negative electrode terminal 82.Specifically, the battery pack includes, inside a housing 70, thefollowing components: a controller 71, an electric power source 72, aswitch 73, a current measurement unit 74, a temperature detector 75, avoltage detector 76, a switch controller 77, a memory 78, a temperaturedetection device 79, and a current detection resistor 80.

The electric power source 72 includes an assembled battery in which twoor more secondary batteries are coupled to each other, and a type of thecoupling of the two or more secondary batteries is not particularlylimited. Accordingly, the coupling scheme may be in series, in parallel,or of a mixed type of both. For example, the electric power source 72includes six secondary batteries coupled to each other in two paralleland three series.

Configurations of the controller 71, the switch 73, the temperaturedetector 75, and the temperature detection device 79 are similar tothose of the controller 66, the switch 67, and the temperature detector69 (the temperature detection device). The current measurement unit 74measures a current using the current detection resistor 80, and outputsa result of the measurement of the current to the controller 71. Thevoltage detector 76 measures a battery voltage of the electric powersource 72 (the secondary battery) and provides the controller 71 with aresult of the measurement of the voltage that has been subjected toanalog-to-digital conversion.

The switch controller 77 controls an operation of the switch 73 inresponse to signals supplied by the current measurement unit 74 and thevoltage detector 76. If a battery voltage reaches an overchargedetection voltage or an overdischarge detection voltage, the switchcontroller 77 turns off the switch 73 (the charge control switch). Thisprevents a charging current from flowing into a current path of theelectric power source 72. This enables the electric power source 72 toperform only discharging through the discharging diode, or only chargingthrough the charging diode. In addition, if a large current flows uponcharging or discharging, the switch controller 77 blocks the chargingcurrent or the discharging current.

The switch controller 77 may be omitted and the controller 71 may thusalso serve as the switch controller 77. The overcharge detection voltageand the overdischarge detection voltage are not particularly limited,and are similar to those described above in relation to the battery packincluding the single battery.

The memory 78 includes, for example, an electrically erasableprogrammable read-only memory (EEPROM) which is a non-volatile memory,and the memory 78 stores, for example, a numeric value calculated by thecontroller 71 and data (e.g., an initial internal resistance, a fullcharge capacity, and a remaining capacity) of the secondary batterymeasured in the manufacturing process.

The positive electrode terminal 81 and the negative electrode terminal82 are terminals coupled to, for example, external equipment thatoperates using the battery pack, such as a laptop personal computer, orexternal equipment that is used to charge the battery pack, such as acharger. The electric power source 72 (the secondary battery) ischargeable and dischargeable through the positive electrode terminal 81and the negative electrode terminal 82.

FIG. 13 illustrates a block configuration of a hybrid automobile whichis an example of the electric vehicle. As illustrated in FIG. 13, theelectric vehicle includes, inside a housing 83, the followingcomponents: a controller 84, an engine 85, an electric power source 86,a motor 87, a differential 88, an electric generator 89, a transmission90, a clutch 91, inverters 92 and 93, and sensors 94. The electricvehicle also includes a front wheel drive shaft 95, a pair of frontwheels 96, a rear wheel drive shaft 97, and a pair of rear wheels 98.The front wheel drive shaft 95 and the pair of front wheels 96 arecoupled to the differential 88 and the transmission 90.

The electric vehicle is configured to travel by using one of the engine85 and the motor 87 as a driving source. The engine 85 is a major powersource, such as a gasoline engine. In a case where the engine 85 is usedas a power source, a driving force (a rotational force) of the engine 85is transmitted to the front wheels 96 and the rear wheels 98 via thedifferential 88, the transmission 90, and the clutch 91, which aredriving parts. Note that the rotational force of the engine 85 istransmitted to the electric generator 89, and the electric generator 89thus generates alternating-current power by utilizing the rotationalforce. In addition, the alternating-current power is converted intodirect-current power via the inverter 93, and the direct-current poweris thus accumulated in the electric power source 86. In contrast, in acase where the motor 87 which is a converter is used as a power source,electric power (direct-current power) supplied from the electric powersource 86 is converted into alternating-current power via the inverter92. Thus, the motor 87 is driven by utilizing the alternating-currentpower. A driving force (a rotational force) converted from the electricpower by the motor 87 is transmitted to the front wheels 96 and the rearwheels 98 via the differential 88, the transmission 90, and the clutch91, which are the driving parts.

When the electric vehicle is decelerated by means of a brake mechanism,a resistance force at the time of the deceleration is transmitted as arotational force to the motor 87. Thus, the motor 87 may generatealternating-current power by utilizing the rotational force. Thealternating-current power is converted into direct-current power via theinverter 92, and direct-current regenerative power is accumulated in theelectric power source 86.

The controller 84 includes, for example, a CPU, and controls an overalloperation of the electric vehicle. The electric power source 86 includesone or more secondary batteries and is coupled to an external electricpower source. In this case, the electric power source 86 may be suppliedwith electric power from the external electric power source and therebyaccumulate the electric power. The sensors 94 are used to control thenumber of revolutions of the engine 85 and to control an angle of athrottle valve (a throttle angle). The sensors 94 include one or more ofsensors including, without limitation, a speed sensor, an accelerationsensor, and an engine speed sensor.

The case where the electric vehicle is a hybrid automobile has beendescribed as an example; however, the electric vehicle may be a vehiclethat operates using only the electric power source 86 and the motor 87and not using the engine 85, such as an electric automobile.

Although not specifically illustrated here, other application examplesare also conceivable as application examples of the secondary battery.

Specifically, the secondary battery is applicable to an electric powerstorage system. The electric power storage system includes, inside abuilding such as a residential house or a commercial building, thefollowing components: a controller, an electric power source includingone or more secondary batteries, a smart meter, and a power hub.

The electric power source is coupled to electric equipment such as arefrigerator installed inside the building, and is couplable to anelectric vehicle such as a hybrid automobile stopped outside thebuilding. Further, the electric power source is coupled, via the powerhub, to a home power generator such as a solar power generator installedat the building, and is also coupled, via the smart meter and the powerhub, to a centralized power system of an external power station such asa thermal power station.

Alternatively, the secondary battery is applicable to an electric powertool such as an electric drill or an electric saw. The electric powertool includes, inside a housing to which a movable part such as adrilling part or a saw blade part is attached, the following components:a controller, and an electric power source including one or moresecondary batteries.

EXAMPLES

A description is given of Examples of the technology of the presentdisclosure according to an embodiment.

Experiment Examples 1 to 16

FIG. 14 illustrates a sectional configuration of a secondary battery ofa coin type for testing. In the following, a negative electrode activematerial was manufactured, following which the secondary battery of thecoin type was fabricated using the negative electrode active material.Thereafter, a battery characteristic of the secondary battery wasevaluated.

As illustrated in FIG. 14, the secondary battery of the coin typeincludes a test electrode 111 inside an outer package cup 114, andincludes a counter electrode 113 inside an outer package can 112. Thetest electrode 111 and the counter electrode 113 are stacked on eachother with the separator 115 interposed therebetween, and the outerpackage can 112 and the outer package cup 114 are crimped to each otherby means of a gasket 116. The test electrode 111, the counter electrode113, and the separator 115 are each impregnated with an electrolyticsolution.

[Manufacture of Negative Electrode Active Material]

First, silicate glass was prepared as a raw material. The kinds ofconstituent elements (excluding oxygen and carbon) and the content (at%) of each of the constituent elements in carbon-reduced silicate glasssynthesized with the silicate glass are as listed in Tables 1 and 2.

As described above, the content of each of the constituent elements ismeasured by analyzing the carbon-reduced silicate glass using SEM-EDX.In the analysis using the SEM-EDX, detection sensitivity to lithium ismarkedly low, and therefore the content of lithium is small enough tohardly affect the content of the second element. Thus, the content oflithium is not listed in Tables 1 and 2.

TABLE 1 Constituent element/Content (at %) First Experiment elementSecond element Third element example Si B P Na K Sc Ti Zr Ce Al S Cl ZnBi Mg Ca Sr Ba 1 98 — 1 1 — — — — — — — — — — — — — — 2 72 15 — 1 4 — —— — 7 — — — — — — — 1 3 55 10 — — — — — — — — — — 3 — 20 — 12  — 4 80 15— — 3 — — — — 2 — — — — — — — — 5 60 — — 1 — 1 1 — — 5 — — 1 —  2 4 10 15  6 60 5 1 3 — — — — — 3 — — 3 — — — — 25  7 60 5 1 1 3 — — — — 20  —— 10  — — — — — 8 65 10 — 1 — — — — — 1 — — — — 10 7 2 4 9 70 25 — 1 2 —— 1 — 1 — — — — — — — — 10 15 20 1 2 — — 4 6 1 5 — — — 45 — — 1 — 11 37— 1 10  22  — 30  — — — — — — — — — — — 12 32 — 2 25  13  — 16  — — 2 —— 1 — — 7 2 — 13 75 2 — 6 5 — — — — 4 1 1 — — — — — 6 16 100 — — — — — —— — — — — — — — — — —

TABLE 2 Raman Capacity Constituent element/Content (at %) XPS spectrum(Si2p) spectrum Charge Discharge retention Experiment First Second ThirdApex Half-width Apex capacity capacity rate example Si element elementelement (eV) Shoulder (eV) S2/S1 (cm⁻¹) (mAh/g) (mAh/g) (%) 1 98 1 1 —103.2 Observed 4.0 0.97 457 1020 500 81 2 72 15 12 1 103.1 Observed 4.70.94 457 1219 620 90 3 55 10 3 32 102.5 Not 2.9 1.82 449 272 130 87observed 4 80 15 5 — 103.8 Observed 4.3 0.85 462 1271 640 91 5 60 — 9 31102.3 Not 2.6 1.72 451 242 106 83 observed 6 60 6 9 25 102.4 Not 2.91.52 450 224 103 86 observed 7 60 6 34 — 103.2 Observed 4.3 0.97 4551016 486 95 8 65 10 2 23 103.3 Not 2.7 0.71 450 281 82 78 observed 9 7025 5 — 103.5 Observed 4.8 0.88 450 1280 644 91 10 15 21 63 1 101.3 Not3.8 1.69 442 418 201 21 observed 11 37 1 62 — 102.9 Not 2.5 0.32 449 875421 61 observed 12 32 2 57 9 103.0 Not 4.3 0.46 445 482 238 84 observed13 75 2 17 6 102.9 Observed 5.2 1.55 454 1173 792 93 14 72 15 12 1 103.2Observed 4.6 0.95 458 1262 610 89 15 72 15 12 1 103.1 Observed 4.7 0.94457 1240 600 91 16 100 — — — 103.0 Observed 5.1 1.61 475 2240 1648 72 *Carbon source: Carbon black (Experiment examples 1 to 13), Polyimide(Experiment example 14), Sucrose (Experiment example 15)

Thereafter, the silicate glass was mixed with a carbon source (carbonblack, which is a carbon material) to thereby obtain a mixture. In thiscase, used as the carbon sources were carbon black (Experiment examples1 to 13), which is a carbon material, and polyimide (Experiment example14) and sucrose (Experiment example 15), which are carbonizable organicsubstances. In addition, the mixing ratio (weight ratio) of the silicateglass to the carbon source was 5:1.

Thereafter, a slurry was prepared by adding a binder solution(N-methyl-2-pyrrolidone solution of polyimide, solid content=18.6%) tothe mixture and stirring the mixture at a (rotation speed of 2000 rpmfor a stirring time of 3 minutes using a stirring device (rotating andrevolving mixer, Awatori Rentaro, manufactured by THINKY Corporation).In this case, the amount of the binder solution added to the mixture was10 weight percent (solid content ratio).

Thereafter, the slurry was dried in an oven at a temperature of 80° C.to obtain a dried product, following which the dried product waspulverized into pulverized flakes.

Thereafter, the pulverized flakes were put into an alumina boat,following which the pulverized flakes were heated at a heatingtemperature of 950° C. for a heating time of 10 hours in an argonatmosphere in a vacuum gas displacement furnace. In this case, thesilicate glass was reduced in the presence of the carbon source (carbonreduction treatment) to synthesize the carbon-reduced silicate glass. Asa result, a center part including the carbon-reduced silicate glass wasformed. Further, a substance such as a decomposition product of thecarbon source (organic substance decomposition carbon) was deposited onthe surface of the center part, forming a covering part. Thus, anegative electrode active material in a flake state was obtained whichincluded the center part and the covering part.

Lastly, the negative electrode active material in the flake state waspulverized in a mortar into the negative electrode active material in apowder state, following which the negative electrode active material inthe powder state was sieved using a mesh (53 μm).

When the state of the negative electrode active material was observedusing a scanning electron microscope (SEM), the negative electrodeactive material remained in the powder state without being melted, eventhough the pulverized frames were heated at a temperature (=950° C.)higher than the glass transition temperature (=about 700° C.) of thesilicate glass in the carbon reduction treatment. The reason for this isconsidered to be that the center part including the carbon-reducedsilicate glass was covered with the covering part.

When the negative electrode active material was analyzed using X-raydiffraction analysis (XRD), a broad halo pattern was detected within therange of 20 from 20° to 25° both inclusive, despite the carbon reductiontreatment of the silicate glass. Accordingly, it was confirmed that thenegative electrode active material (carbon-reduced silicate glass) hadnot been crystallized.

When the negative electrode active material was analyzed using Ramanspectroscopy, distinct G and D bands were detected in the Ramanspectrum. Accordingly, it was confirmed that the center part was coveredwith the covering part including carbon as a constituent element.

The results of analysis of the negative electrode active material usingXPS are as listed in Table 2. In this case, the position of the apex XAT(binding energy: eV), the presence or absence of the shoulder XAS, thehalf-width of the peak XA (eV), and the area ratio S2/S1 were examinedon the basis of the result of analysis of the negative electrode activematerial (XPS spectra of Si2p illustrated in FIG. 2) in accordance withthe procedure described above.

The results of analysis of the negative electrode active material usingRaman spectroscopy are as listed in Table 2. In this case, the positionof the apex RAT (Raman shift: cm⁻¹) was examined on the basis of theresult of analysis of the negative electrode active material (Ramanspectra illustrated in FIG. 3) in accordance with the proceduredescribed above.

The test electrode 111 was fabricated and an electrolytic solution wasprepared, following which the secondary battery of the coin type wasassembled in accordance with the following procedure.

Here, a negative electrode was fabricated as the test electrode 111.First, the negative electrode active material described above, anegative electrode binder precursor (polyamic acid solution (polyimideprecursor), U-varnish-A, manufactured by Ube Industries, Ltd.), and anegative electrode conductor (carbon powder KS6 manufactured by TIMCALCo., Ltd., and acetylene black, Denca black (registered trademark)manufactured by Denka Co., Ltd.) were mixed to thereby obtain a negativeelectrode mixture. In this case, the mixing ratio (mass ratio) among thenegative electrode active material, the negative electrode binderprecursor, and two kinds of negative electrode conductors was7:0.5:1:0.25. Thereafter, the negative electrode mixture was put into anorganic solvent (N-methyl-2-pyrrolidone), following which the organicsolvent was stirred to thereby prepare a negative electrode mixtureslurry in a paste state.

Thereafter, the negative electrode mixture slurry was applied to oneside of a negative electrode current collector (copper foil,thickness=15 μm) using a coating apparatus, following which the negativeelectrode mixture slurry was heated and dried (heating temperature=425°C.) in a vacuum sintering furnace. A negative electrode binder(polyimide) was thereby synthesized, forming a negative electrode activematerial layer including the negative electrode active material, thenegative electrode binder, and the negative electrode conductor. Lastly,the negative electrode current collector on which the negative electrodeactive material layer had been formed was punched into a disk shape(outer diameter=15 mm), and the punched negative electrode activematerial layer was compression-molded using a roll pressing machine. Asa result, the test electrode 111 which is the negative electrode wasfabricated.

Note that, a test electrode 111 for comparison was prepared (Experimentexample 16) by a similar procedure except that another negativeelectrode active material (silicon monoxide (SiO)) was used instead ofthe negative electrode active material described above.

As the counter electrode 113, a lithium metal plate was used. In thiscase, lithium metal foil was punched into a disk shape (outerdiameter=15 mm).

An electrolyte salt (lithium hexafluoride phosphate) was added to asolvent (ethylene carbonate, fluoroethylene carbonate, and dimethylcarbonate), following which the solvent was stirred. In this case, themixing ratio (mass ratio) of the solvent among ethylene carbonate,fluoroethylene carbonate, and dimethyl carbonate was 40:10:50. Thecontent of the electrolyte salt was 1 mol/kg with respect to thesolvent.

First, the test electrode 111 was housed inside the outer package cup114, and the counter electrode 113 was housed inside the outer packagecan 112. Thereafter, the test electrode 111 housed inside the outerpackage cup 114 and the counter electrode 113 housed inside the outerpackage can 112 were stacked on each other with the separator 115(microporous polyethylene film, thickness=5 μm), impregnated with theelectrolytic solution, interposed therebetween. Thus, the test electrode111 and the counter electrode 113 were each impregnated with a portionof the electrolytic solution contained in the separator 115. Lastly, theouter package can 112 and the outer package cup 114 were crimped to eachother by means of the gasket 116 in a state where the test electrode 111and the counter electrode 113 were stacked on each other with theseparator 115 interposed therebetween. Accordingly, the test electrode111, the counter electrode 113, the separator 115, and the electrolyticsolution were sealed by the outer package can 112 and the outer packagecup 114. As a result, the secondary battery of the coin type wascompleted.

Evaluation of a battery characteristic (a charging characteristic, adischarging characteristic, and a cyclability characteristic) of thesecondary batteries revealed the results listed in Table 2.

In a case of examining the battery characteristic, first, the secondarybattery was charged and discharged for one cycle in an ambienttemperature environment (temperature=23° C.) to stabilize a state of thesecondary battery. Thereafter, the secondary battery was charged in thesame environment, and a second-cycle charge capacity (mAh) was measured.A charge capacity per unit weight (mAh/g) was thereby calculated on thebasis of the weight (g) of the negative electrode active material inorder to evaluate the charge characteristic.

Thereafter, the secondary battery in a charged state was discharged inthe same environment, and a second-cycle discharge capacity (mAh) wasmeasured. A discharge capacity per unit weight (mAh/g) was therebycalculated on the basis of the weight (g) of the negative electrodeactive material in order to evaluate the discharge characteristic.

Thereafter, the secondary battery was repeatedly charged and dischargedin the same environment until the total number of cycles of charging anddischarging reached 100 cycles, and a 100th-cycle discharge capacity(mAh) was measured. Lastly, to evaluate the cyclability characteristic,a capacity retention rate was calculated as follows: capacity retentionrate (%)=(100th-cycle discharge capacity (mAh)/second-cycle dischargecapacity (mAh))×100.

Upon charging, the secondary battery was charged with a constant currentof 0.1 C until the voltage reached 4.20 V, following which the secondarybattery was charged with a constant voltage of 4.20 V until the currentreached 0.05 C. Upon discharging, the secondary battery was dischargedwith a constant current of 0.1 C until the voltage reached 2.50 V. “0.1C” refers to a value of a current that causes a battery capacity(theoretical capacity) to be completely discharged in 10 hours, and“0.05 C” refers to a value of a current that causes the battery capacitydescribed above to be completely discharged in 20 hours.

As apparent from Tables 1 and 2, the battery characteristic of thesecondary battery greatly varied depending on the composition and thephysical property of the negative electrode active material.

Specifically, in a case where the composition of the negative electrodeactive material satisfied the following constitutional conditions andwhere the results of analysis of the negative electrode active materialusing XPS and Raman spectroscopy (the XPS spectrum of Si2p and the Ramanspectrum) satisfied the following physical property conditions (e.g.,Experiment example 1), a high capacity retention rate was obtained whilea high charge capacity and a high discharge capacity were securedregardless of the kind of the carbon source, as compared with a casewhere the constitutional conditions and the physical property conditionswere not satisfied (e.g., Experiment example 3).

The constitutional conditions regarding the composition of the negativeelectrode active material are as follows: The negative electrode activematerial includes silicon, oxygen, the first element, the secondelement, and the third element as constituent elements. The content ofsilicon with respect to all of the constituent elements excluding oxygenand carbon is 60 at % or greater and 98 at % or less. The content of thefirst element with respect to all of the constituent elements excludingoxygen and carbon is 1 at % or greater and 25 at % or less. The contentof the second element with respect to all of the constituent elementsexcluding oxygen and carbon is 1 at % or greater and 34 at % or less.The content of the third element with respect to all of the constituentelements excluding oxygen and carbon is 0 at % or greater and 6 at % orless.

The physical property conditions regarding the results of analysis ofthe negative electrode active material are as follows: In the XPSspectrum (Si2p) measured using XPS, the peak XA is detected which hasthe apex XAT (at a position within a range of the binding energy from102 eV to 105 eV both inclusive) and the shoulder XAS illustrated inFIG. 2. In addition, in the Raman spectrum measured using Ramanspectroscopy, the peak RA is detected which has the apex RAT (at aposition within a range of the Raman shift from 435 cm⁻¹ to 465 cm⁻¹both inclusive) illustrated in FIG. 3.

In particular, in a case where the above-described constitutionalconditions regarding the composition of the negative electrode activematerial were satisfied and where the above-described physical propertyconditions regarding the results of analysis of the negative electrodeactive material were satisfied, a high capacity retention rate wasobtained together with a sufficient charge capacity and a sufficientdischarge capacity if the half-width was 4.0 eV or greater or the arearatio S2/S1 was 0.85 or greater.

In the case where the above-described constitutional conditionsregarding the composition of the negative electrode active material weresatisfied and where the above-described physical property conditionsregarding the results of analysis of the negative electrode activematerial were satisfied, substantially similar performance was obtained,as compared with a case where an existing other negative electrodeactive material (SiO) was used (Experiment example 16).

Specifically, in a case where the negative electrode active materialsatisfying the constitutional conditions and the physical propertyconditions described above was used, each of the charge capacity and thedischarge capacity was decreased, as compared with the case where theother negative electrode active material was used. However, each of thecharge capacity and the discharge capacity was sufficiently high withinan acceptable range.

Moreover, in the case where the negative electrode active materialsatisfying the constitutional conditions and the physical propertyconditions described above was used, the capacity retention rate wasgreatly increased, as compared with the case where the other negativeelectrode active material was used.

Accordingly, in the case where the negative electrode active materialsatisfying the constitutional conditions and the physical propertyconditions described above was used, the capacity retention rate wasmarkedly improved while each of the charge capacity and the dischargecapacity was secured, as compared with the case where the other negativeelectrode active material was used.

As in the results listed in Tables 1 and 2, in the case where theabove-described constitutional conditions regarding the composition ofthe negative electrode active material were satisfied and where theabove-described physical property conditions regarding the results ofanalysis of the negative electrode active material were satisfied, asuperior cyclability characteristic was obtained together with asuperior charge characteristic and a superior discharge characteristic.Accordingly, a superior battery characteristic was obtained in thesecondary battery.

Although the technology has been described above with reference to theembodiments and Examples, configurations of the technology are notlimited to those described with reference to the embodiments andExamples above, and are therefore modifiable in a variety of ways.

Specifically, although the description has been given of the case wherethe liquid electrolyte (electrolytic solution) and the gel electrolyte(electrolyte layer) are used, the electrolyte is not limited to aparticular kind. Alternatively, an electrolyte in a solid state (solidelectrolyte) may be used.

Moreover, although the description has been given of the case where thestructure of the secondary battery is of the laminated-film type, thecylindrical type, or the coin type, the structure is not limited to aparticular structure. Alternatively, the secondary battery may haveother structures including, without limitation, those of a prismatictype and a button type.

Moreover, although the description has been given of the case where thestructure of the battery device is of the wound type or the stackedtype, the structure of the battery device is not limited to a particularstructure. Alternatively, the battery device may have other structuresincluding, without limitation, those of a zigzag folded type in whichthe electrodes (the positive electrode and the negative electrode) arefolded in a zigzag manner.

Further, although the description has been given of the case where theelectrode reactant is lithium, the electrode reactant is not limited toa particular element. Specifically, the electrode reactant may beanother alkali metal such as sodium or potassium, or may be an alkalineearth metal such as beryllium, magnesium, or calcium, as describedabove. Alternatively, the electrode reactant may be another light metalsuch as aluminum.

Note that the effects described herein are mere examples, and effects ofthe technology are therefore not limited to those described herein.Accordingly, the technology may achieve any other suitable effectaccording to an embodiment.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. An active material comprising, as constituent elements: silicon (Si);oxygen (O); a first element including boron (B), phosphorus (P), orboth; a second element including at least one of an alkali metalelement, a transition element, or a typical element, the typical elementexcluding silicon, oxygen, boron, phosphorus, an alkali metal element,and an alkaline earth metal element; and a third element including analkaline earth metal element, wherein a content of silicon with respectto the constituent elements excluding oxygen and carbon (C) is 60 atomicpercent or greater and 98 atomic percent or less, a content of the firstelement with respect to the constituent elements excluding oxygen andcarbon is 1 atomic percent or greater and 25 atomic percent or less, acontent of the second element with respect to the constituent elementsexcluding oxygen and carbon is 1 atomic percent or greater and 34 atomicpercent or less, a content of the third element with respect to theconstituent elements excluding oxygen and carbon is 0 atomic percent orgreater and 6 atomic percent or less, a first peak is detected in an XPSspectrum of Si2p relating to the active material, the XPS spectrum ofSi2p being measured using X-ray photoelectron spectroscopy (XPS) anddefined by a horizontal axis indicating a binding energy (electronvolt)and a vertical axis indicating a spectrum intensity, the first peakincluding an apex within a range of the binding energy of 102electronvolts or greater and 105 electronvolts or less, and a shoulderon a smaller binding energy side of the apex, and a second peak isdetected in a Raman spectrum relating to the active material, the Ramanspectrum being measured using Raman spectroscopy and defined by ahorizontal axis indicating a Raman shift (cm⁻¹) and a vertical axisindicating a spectrum intensity, the second peak including an apexwithin a range of the Raman shift of 435 cm⁻¹ or greater and 465 cm⁻¹ orless.
 2. The active material according to claim 1, wherein the firstpeak has a half-width of 4.0 electron volts or greater.
 3. The activematerial according to claim 1, wherein, in a case where the first peakis decomposed into a Si⁰ peak, a Si¹⁺ peak, a Si²⁺ peak, a Si³⁺ peak,and a Si⁴⁺ peak, a ratio S2/S1 of a sum S2 of an area of the Si⁰ peak,an area of the Si¹⁺ peak, an area of the Si²⁺ peak, and an area of theSi³⁺ peak to an area Si of the Si⁴⁺ peak is 0.85 or greater.
 4. Theactive material according to claim 1, comprising: a center partincluding silicon, oxygen, the first element, the second element, andthe third element as constituent elements, wherein the first peak isdetected in the XPS spectrum relating to the active material, and thesecond peak is detected in the Raman spectrum relating to the activematerial; and a covering part covering at least a portion of a surfaceof the center part and including carbon as a constituent element.
 5. Amethod of manufacturing an active material, the method comprising:preparing silicate glass including, as constituent elements, silicon(Si), oxygen (O), a first element including boron (B), phosphorus (P),or both, a second element including at least one of an alkali metalelement, a transition element, or a typical element, the typical elementexcluding silicon, oxygen, boron, phosphorus, an alkali metal element,and an alkaline earth metal element, and a third element including analkaline earth metal element; mixing the silicate glass with a carbonsource to thereby obtain a mixture of the silicate glass and the carbonsource; and heating the mixture to thereby manufacture the activematerial including silicon, oxygen, the first element, the secondelement, and the third element as constituent elements, wherein, in theactive material, a content of silicon with respect to the constituentelements excluding oxygen and carbon (C) is 60 atomic percent or greaterand 98 atomic percent or less, a content of the first element withrespect to the constituent elements excluding oxygen and carbon is 1atomic percent or greater and 25 atomic percent or less, a content ofthe second element with respect to the constituent elements excludingoxygen and carbon is 1 atomic percent or greater and 34 atomic percentor less, and a content of the third element with respect to theconstituent elements excluding oxygen and carbon is 0 atomic percent orgreater and 6 atomic percent or less.
 6. The method of manufacturing theactive material according to claim 5, wherein the carbon source includesa carbon material, a carbonizable organic substance, or both.
 7. Anelectrode comprising an active material according to claim
 1. 8. Asecondary battery comprising: a positive electrode; a negative electrodeincluding a negative electrode active material; and an electrolyticsolution, wherein the negative electrode active material includes, asconstituent elements, silicon (Si), oxygen (O), a first elementincluding boron (B), phosphorus (P), or both, a second element at leastone of an alkali metal element, a transition element, or a typicalelement, the typical element excluding silicon, oxygen, boron,phosphorus, an alkali metal element, and an alkaline earth metalelement, and a third element including an alkaline earth metal element,a content of silicon with respect to the constituent elements excludingoxygen and carbon (C) is 60 atomic percent or greater and 98 atomicpercent or less, a content of the first element with respect to theconstituent elements excluding oxygen and carbon is 1 atomic percent orgreater and 25 atomic percent or less, a content of the second elementwith respect to the constituent elements excluding oxygen and carbon is1 atomic percent or greater and 34 atomic percent or less, and a contentof the third element with respect to the constituent elements excludingoxygen and carbon is 0 atomic percent or greater and 6 atomic percent orless, a first peak is detected in an XPS spectrum of Si2p relating tothe active material, the XPS spectrum of Si2p being measured using X-rayphotoelectron spectroscopy (XPS) and defined by a horizontal axisindicating a binding energy (electronvolt) and a vertical axisindicating a spectrum intensity, the first peak including an apex withina range of the binding energy of 102 electronvolts or greater and 105electronvolts or less and a shoulder on a smaller binding energy side ofthe apex, and a second peak is detected in a Raman spectrum relating tothe active material, the Raman spectrum being measured using Ramanspectroscopy and defined by a horizontal axis indicating a Raman shift(cm⁻¹) and a vertical axis indicating a spectrum intensity, the secondpeak including an apex within a range of the Raman shift of 435 cm⁻¹ orgreater and 465 cm⁻¹ or less.
 9. The secondary battery according toclaim 8, wherein the secondary battery comprises a lithium-ion secondarybattery.